I dont know why you think you need to mask all of these.
They can just be disabled … if they are starting while disabled then you probably want to disable whatever is starting them too (or you realize you actually dont want to disable them at all)
As to snapd … thats up to you … if you use snaps you probably want to keep it.
If not … you should probably remove all snap related packages … at which point the service should not still exist. Though you could double-check to disable it as well.
No. It is not.
Unless you plan on manually handling that journal flush yourself you shouldnt touch that.
I get the feeling you found out about disabling services and now you are just shooting wildly.
It would probably better serve you to get a handle on what all these things are, what you want to achieve, and whether disabling every service in sight is actually the best way to go about it.