With regards to frame rate:
Over or under cranking has been routine in movie making since the 1930s.
The frame rate has a lot to do with the emotional response you get from the motion picture and has little to do with how we make judgement about "realism"
Slow frame rates garner soft images that are often referred to as "film like". People often assume that film has great resolution. Classic 24 fpm film is usually shot with a slow shutter speed and each frame has a soft blur on any thing moving in the frame. Some folks think it gives a deluxe vibe, and they describe it as "film like". It's important to note that each frame can seem blurry while the motion picture or stream does not seem blurry to the viewers eyes. One can only sense the 'vibe".
High frame rates have to be shot with faster shutter speeds so you get sharper images when there is movement. It provides a more aggressive vibe that can help add tension to a sequence. fast shutter speeds are popular in sports because it makes stuff seem exciting.
The thing to appreciate is that we watch movies AFTER they have been conformed to presentation frame rates.
What that means is that there is one frame rate for capture and then another frame rate for presentation. You can do several things when you are "conforming" to another frame rate to achieve different effects.
One of the most time honored techniques is to under crank action sequences so that they are sped up for the presentation and seem more exciting. This is done routinely but subtlety... have you ever noticed how a fight scene in a great movie seems so exciting but if you see a behind the scene video of the movie being made it seems the "fight acting" is slow and almost comical. That is the magic of under cranking.
The other famous effect is over cranking where you shoot at a higher rate and then get a slow motion effect in presentation that adds drama and seriousness to a sequence. If it's done subtler it just lends itself to the story telling and if it's done overtly it looks like "slow motion". It's a common film making technique.
If you simply shoot at a different rate with out intent to achieve a motion effect then you can use modern digital compositing tools to "conform" the source footage to some target frame rate. So for example you can shoot fast shutter speed at 60fps and later conform the whole thing to 24fps by stacking frames and throwing out info. This has some benefits for basic story telling as it gives you some control in post over the look or feel of the sequence.
It also gives you clean sharp images for digital compositing tasks such as green screen keying... the types of things that classic 24p soft look film is not ideal at.
Then after you use the sharp imagery to do all the digital post work you may conform down to 24p and purposefully "blur' it up a bit so it looks deluxe and "film like".
Conforming has been around a long time as it has been used to convert 24p films to 29.97 TV for decades. Now there are lots more reasons to conform... there is just so much variety that conforming has become sort of routine.
To make it more confusing... most actual film theaters display 24p film with double taps... in other words we see 48 flickers that are made up of 24 frames each flashed at us twice. This is totally different than the 24 24p flashes we see on our BluRay big screen TVs.... so when lots of people talk about 24p and a theatrical "film look" it can be kinda confusing to know what they think they are speaking of.
Random thoughts.
best regards,
mike