Maybe just disabling the "Flip" command would be enough, or is there a better way?
You could skip pretty much all drawing altogethr, for the most part.
As far as having server vs. client side collision checks: Keep in mind that there is latency with the network communications - you'll likely need to do some predictive work and such to make sure everything draws smoothly without excessive jumping around, so you may need to do your checks on both sides and communicate to find the 'true' state of things.
something else to remember, is that you can't always trust the information that the client sends, so the server may need to have some safeguards to double-check what's going on to verify that what just happened is even possible. (to prevent individual patched clients from cheating, e.g. by moifying their movement speeds, amount of ammo, health, etc.)