Sanderxpander's right.
Sonar, like most DAWs, asks the ASIO driver, Core Audio, whatever, what the set latency is, plus you have the option of adjusting that figure in Sonar's preferences if it's noticeably incorrect, which doesn't happen very often.
What this means is that Sonar then automatically corrects for latency when placing audio on the time-line. It also compensates for a plugin's own latency as well, and usually gets it right unless the plugin is really badly written. All done automatically.
Latency affects the time when we hear something while we are playing or mixing. It almost never* affects where the audio is placed in time or what the mix sounds like after the pass the automation was written, the fader moved etc. other than if there are plugins that require say 50ms to do their thing Sonar will delay commencing playback by 50ms to give that plugin a chance to get up to speed before everything happens. You probably won't notice even that, especially as Sonar has a default start delay of 250ms so it can read and process the first chunks of MIDI tracks.
*there are times a DAW gets it wrong, but mostly that's when you're using MIDI to drive external hardware synths and the software doesn't know how long it takes that synth to produce a sound after it gets the MIDI. But even then it's a matter of a few milliseconds at most.
Edited to add - in response to your original question, Platinum feels "snappier" than X3 to me, but there's no audio latency difference I've noticed. I just leave the UFX at 64 samples at 44.1KHz and pretty much forget about it. I could run X3 or Plat at the lowest latency the UFX driver allows, but all that results in is having to start increasing the latency a bit as the project grows. So I might as well start where I will end up anyway.