In determining the appropriate volume levels for each track of my project (and the overall mix itself), I cannot help but feel overwhelmed and confused by the many methods of adjusting volume. Also, I require further understanding of what the digital peak should be.
 
Volume
There are several volume levers throughout the software environment. Here is a brief list of the components' volume levers and their default setting:
Sonar Track Pane & Inspector Pane (same): 0 dB
Cakewalk SoundCenter: Around 75%
SI Drums: Variable with drum kit
Session Drummer: 0dB
TTS-1: 100/127
 
In addition, I have my external speaker volume and Windows mixer volume set at 50%.
 
Digital playback meters
Throughout the years, I've become accustomed to a digital meter of red/yellow/green, but Sonar uses orange/bright green. Some components (like SI Drums) use red/orange.
 
Questions:
1) Which of Sonar's volume levers should I be primarily utilizing (and which levers not to touch)?
2) How do I know where the appropriate volume should be according to the digital playback meters?
 
Thanks in advance for any clear, straightforward answers to my questions.

You playback system is not part of the finished output to an exported wave file.  A lot of folks make the mistake of not setting their monitor levels correctly so they make errors in tracking volume etc. Take the time to set your monitor levels to match the output peak. In other worlds, if it's near the red it will be loud. There is a system called the K system that is excellent if your not sure about these things. I don't use it only because I get good results using my ears. But it is a good system. 
 
Tracking- 
Don't go over the top. Keep to safe levels because it's digital and you need not run your tracks hot. I don't use numbers so sorry I can't help with that. I just aim for my tracks being at the top of the Green zone. That works for me for the last 35 years. 
If a track is recorded with a wimpy volume level I'll either apply "gain" ( under process /audio ) or pump the Trim a bit.
 
And midi synths for the most part we do not have to touch the GUI volume pre sets. leave them at unity.  The one to pay attention to is the soft synth audio track and you treat it like any other audio track. For the most part mixing is done with the track faders.  
I don't worry about pushing things to the top until I master. Then I look at the numbers. Very very closely. Don't try and master while mixing. Mixing and Mastering are two entirely different steps. 

Faders are your first vol control.  The sound comes in and the faders are at unity (or 0 dBs - adding and subtracting nothing).  The first thing I do is put up a rough mix by ear, adjusting the vol via faders.  Actually, I usually mix a bit while composing to get a sense of the song.  The alternate methods of vol control, like gain (trim) or make-up gain in comps, come after the vol and automation of same.
 
External synths are usually set to 75% or so of the maximum - I've always found that is close to the optimum for gainstaging both for internally for the synth and for input - that gives you gain to add w/ the DAW fader or to come down from.  Most softsynths are pretty much too loud when first open them, so if the vol knob is easily accessed I'll use that or adjust the vol of the DAW fader.
 
The monitoring system is really one you have to learn - there are no rules unless you set up for the K-system, and it is pretty specific and came out of film.  Although there is no average vol level to set your monitors to, although there are endstops to what works.  Too loud and you can't set track levels properly for quieter systems and the vocals and leads will be too low.  Set the monitors too soft and they'll be too loud at louder listening levels.  Too loud and you'll burn out your ears faster during a session.  Too soft and you'll burn out trying to concentrate and hear into the music.  It is a judgment call from both experience and "your personal style."
 
@

The OP's right: there are indeed a very large number of factors that affect volume, and it can be a challenge to keep track of them all. 
 
In fact, with the exception of processors that add content (e.g. reverbs and delays), every process a mix undergoes involves multiplication of values that affect volume.
 
One way to manage it all is to limit the number of discreet volume controls you touch in the chain. If your equalizer has an output level knob, leave it at 0dB. Use a compressor's gain compensation just for compensation and not for setting levels. Use a soft synth's volume control rather than any of the subsequent audio effects. And keep everything under -12 dB along the way.
 
Your playback system also plays a role in all this. If you're monitoring too quietly you'll tend to make individual tracks too loud. That's why you always want to monitor at a consistent volume, which is what the K-system is all about.
 
As for overall levels, just make sure peaks (on the master bus) never exceed -3dB prior to mastering. If you do that, then the only way you can subsequently screw it up is in the mastering, and you can always have somebody else do that for you if necessary.

AT
Faders are your first vol control.  The sound comes in and the faders are at unity (or 0 dBs - adding and subtracting nothing).  The first thing I do is put up a rough mix by ear, adjusting the vol via faders.  Actually, I usually mix a bit while composing to get a sense of the song.  The alternate methods of vol control, like gain (trim) or make-up gain in comps, come after the vol and automation of same.
 
External synths are usually set to 75% or so of the maximum - I've always found that is close to the optimum for gainstaging both for internally for the synth and for input - that gives you gain to add w/ the DAW fader or to come down from.  Most softsynths are pretty much too loud when first open them, so if the vol knob is easily accessed I'll use that or adjust the vol of the DAW fader.
 
The monitoring system is really one you have to learn - there are no rules unless you set up for the K-system, and it is pretty specific and came out of film.  Although there is no average vol level to set your monitors to, although there are endstops to what works.  Too loud and you can't set track levels properly for quieter systems and the vocals and leads will be too low.  Set the monitors too soft and they'll be too loud at louder listening levels.  Too loud and you'll burn out your ears faster during a session.  Too soft and you'll burn out trying to concentrate and hear into the music.  It is a judgment call from both experience and "your personal style."
 
@

Actually the signal first goes through the input gain/trim control at the top of the channel strip
 
To the OP - please be aware that NONE of the controls inside Sonar can affect your levels when recording. You can only set input levels outside of Sonar before the signal hits your converters. If it's too hot coming in you will clip  the signal and you'll have ruined your recording.
 
The usual place to adjust your input levels is at your interface.
 
Once you've got a a decent level coming in (Goldilocks level, not too hot, not too cold - anywhere between -6 & -15dB is fine) you'll find when you come to mix things will be a whole lot easier.
 
This is know as Gain Staging - you can read loads about this, here's a very good starter:
 
http://www.soundonsound.com/sos/sep13/articles/level-headed.htm
 
 

Thank you for your answers on this, guys! I appreciate the input.
 
Although much of what was said is a little over my head, I think the answer I understand best is Bitflipper's. I'm an amateur musician (I admit to that openly and freely) and I'm still learning new things all the time.
 
What I do by habit is set my external pair of desktop speakers to 50%. My Windows mixer is at 50% also. That just seems like logic to me. On the other hand, what you're all saying is 1) not overthink it, 2) only utilize main volume control (master & tracks) and not obsess over synth volume faders? I also learned in a YouTube mixing video that a good place to set Master is at -9dB before I get comfortable mixing the levels of the other tracks...
 
That's what I'm getting and it sounds like it makes sense. Thanks again! :)

I try to stage gain as early in the signal path as possible, shooting for around -15 dBs with faders at unity and I adjust things at or prior to the audio interface when possible, and for soft synths I even adjust their volume using the master volume of the synth, rather than the Sonar Input Trim.
 
Bob Bone