with FXOpen, i don't think there is technically a site-enforced minimum. offers from PAMM master accounts enforce their own minimums. some have a $1 minimum, others a $50k minimum.
side note: i'm not sure they actually accept bitcoin directly. you might need to deposit through neteller, skrill, etc and then transfer to FXOpen.
i don't think any of the terms have been finalized at geco. it hasn't launched yet.
one more option i came across is FIBO group. i don't know much about them except they are registered in the BVI, they offer PAMM accounts, and they have 9 crypto markets. they accept bitcoin deposits via bitpay or the blockchain.com API and they do direct bitcoin withdrawals.