1.

#Damus is iOS only (for now), no KYC, self-funded (as far as I know of today), OG Nostr client

#primal is iOS, android and webapp, KYC wallet (use strike as backend), vc-funded

2.

Zaps go to whatever lightning wallet you connected to your Nostr account (can't zap u unless you have LNURL or ⚡@ddress listed) I see you have strike rn

3.

Relays can see 100% of everything you do, how long you look at note, 100% of your drafts, etc.