Lots of people get groups and vca faders mixed up. Real music passes through a group fader. You can do things like add processing or eq to that group, but a vca is a remote way of just accessing loads of faders at the same time. Assigning all your drums to a vca just makes your eight or more faders for each source go up and down at the same time. It’s just a remote control. It cannot change the sound. That is done somewhere else. You can’t add effects to a vca because it is just control. Oddly, on some systems, you could add a reverb return fader to a vca I suppose but I’m not sure why you would do that?

Right. My question is about assigning a submix bus to a VCA. 

Example. If I have 4 kik drum tracks, and 3 snares each feeding their own kik/snare buss. These busses each have some compession on them. And the busses feed a "drums" sub mix bus, which also has more compression on it.

Now when I turn up the one of the individual 4 kik drum track faders, to make it louder, I'm also feeding more level to the kik drum bus compressor. This will result in more compression unless I adjust the input gain. Ditto for the drums bus.

What I'm looking for is a way to increase the volume of a track or sub mix, without messing up the gain staging of all the compressors ect that those tracks/busses feed into.

So if a VCA is just a volume knob essentially, then it would make sense to use a VCA for this purpose. What I'm not sure of is if that VCA volume adjustment would bypass any of the bussing or not. Put another way, would it simply amplify the signal it's assigned to, or would it increase it's gain at the track level, thus altering the gain stages that follows it 

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Ive been grouping all my tracks and instrument types into sub group busses for a while now, since I like the results, and I can apply compression in stages, and summing happens along the way as opposed to at the master (I think anyway).

So I just want to be able to adjust volume, without adding in more compression or having to adjust input gains on every bus that follows.

You just allocate the vca to whichever fader, or faders you would push in real life. If you had to do it manually, find the faders, and then map those. Nothing then changes. You would also then be able to keep any stereo panning too. 

Would that feed more signal to the master bus processing?

It would do whatever pushing the real faders would do. It's simply a remote control.