It really depends on your driver and their preferences. Generally, the viable range for drivetrain speeds is in-between 52 (ish) inches per second to around 80 inches per second. Generally, for teams that are just starting out, I would place the limit on drivetrain speed at around 65 inches per second, anything faster can be way too hard to control.
Using blue motors is also better than using red or green motors, since you can gear up using blue motors. For example, look at any drivetrain using green motors here: Catalogue of Drive Gearings Notice how the bigger gears are on the outsides of the wheels. For some forms of elevation, using green motors would cause a lot of issues because of this. If you look at any drivetrain gearing that uses blue motors, the bigger gears are hidden, making elevation tasks easier, and sometimes actually possible. Not to mention, gearings that use Green motors are also more bulky, which can be a deal breaker for some drivetrain sizes. Using green motors for a drivetrain is okay, but avoid it if you can.
In terms of wheels, you can use any of them and have a good time. However, if you can avoid 4 inch wheels, do that. It can limit wheel placements, your robot drivebase would be higher off the ground, (a deal breaker for some teams as well), and it limits you gearing options a little too much in my opinion. 4 inch wheels can be used well, but you have better options if you can make use of them. In terms of what kind of wheels to actually use (Omni wheels or a mix of traction wheels and Omni wheels), it depends on your drivers preferences and what wheels you have. Generally, if you want traction wheels, put them somewhere in the middle of your drivetrain (whether it is directly in the middle or offset in the middle). And, please, don’t make the mistake of making your drivetrain all traction wheels.
Drivetrain size varies… a lot. For almost any team, I would say any drivebase size from 27 holes by 27 holes (13.5 in by 13.5 in) to 32 holes by 32 holes (16 in by 16 in). Anything smaller than 25 hole by 25 holes or anything bigger than 33 by 33 holes may be too limiting. This will heavily depend on your gearing and wheels, so figure out what gearing you want before you figure out the size of your drivebase.
Sorry I said a lot of words, but there are a lot of variables to consider for drivetrains. Good luck out there.