Do look at crypto acquisition guide. And see this topic here.
I wouldn’t consider SEPA transfer to a centralized entity totally anonymous. But stil would be much better option than handing out your kyc to yet another entity.
Not sure how tolerant revolut is with crypto transactions. But i don’t see much value in doing fiat-crypto pairs on Bisq. P2P transactions requires a degree of trust from the sellers side , as they would be knowing exactly who paid them. So you can’t guarantee if the other party is trustable and won’t be maintaining any unofficial database of usernames with their banking name. (Which actually is happening a lot and traders maintain unofficial database often shared with other traders)
So for XMR-Fiat pairs , Bisq and localmonero would provide almost same privacy.
p2p transaction though are private but in practical scenario involves much more
hassle with you on a constant lookout for various scams , people asking for kyc , and in many situations would involve significant markup in prices.
yeah if monero is your final target then it makes less sense to acquire BTC first, as BTC may involve significant fees and may do very less to add to your privacy.
If you want to hide the fact that you had bought X amount of crypto from your government, then i would only prefer going for cash payments.