Onboarding friction and hidden costs with prop firms?

Been looking into scaling up with a prop firm, but I'm getting bogged down in the details beyond just the challenge. Specifically, I'm trying to get a handle on the real friction points during onboarding – KYC/KYB seems to be a mixed bag depending on the firm, some are slick, others feel like they're still in the dark ages. Beyond that, what's everyone's experience with the actual spreads and fees once you're live? Many advertise tight spreads, but then you dig a bit and find commissions or overnight fees that can eat into profits, especially on $EURUSD or indices. And on the flip side, the payout process – how smooth is it? Are there any common traps to watch out for regarding withdrawal limits or processing times? Trying to avoid signing up only to find the hidden costs or payout headaches negate the upside.