Well I am worried because I already got kicked off of Gemini. But maybe they have more stringent standards? I will be dealing with large amounts, what kind of extra verification would they require?
The source of funds would definitely be something they want to see. Where did the crypto come from? where did the fiat come from? They can however and probably will drag this for a very long time (and we have seen many cases where this happens in the past).
So again, if you're not willing to provide any of this stuff to them or you just don't want to deal with the headache and end up making multiple Reddit posts about this matter on /r/CryptoCurrency, /r/Kraken or /r/Bitcoin, tagging them on Twitter, and opening a scam accusation in bitcointalk etc. You should probably just stay away. I know I wouldn't deal with a fiat exchange with large sums of money.
And then of course, if you're cashing out for fiat, you should probably expect a call from the bank as well. Unless you're used to transfer large sums of money and the bank is crypto friendly.
What proof do they require? Seeing my tax returns for my income as well as the initial buys of the crypto from Gemini? You say to avoid these kyc cex, but how else can I sell for fiat and then send to my bank account?