Well TBH the hop up and barrel are probably easier to upgrade than anything else. Once you get into compression parts you're talking about getting into the gearbox and it's something I wouldn't recommend a newbie do especially with a V7 gearbox.
As for parts, they're totally TM compatible (supposedly even moreso than G&P) and yes they are a "knockoff brand" or in the airsoft world as we call it ACM (All China Made) or a "clone", not technically a knockoff because they're not purporting to be TM or whatever (if CYMA is a knockoff then technically VFC, G&P, CA, KA, etc. are also knockoffs too). BTW Echo1 rebrands CYMA (some say with an extra QC check or possibly higher "binned" parts but I'm not sure if it's a rumour or true or if someone just made that up to feel good about their purchase).
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE