I am sure there will be a market for frex with crypto eventually, instead of spending dollars or any other fiat you use, you will be capable of spending bitcoin on the moves you make, it will probably exactly be like any other forex website but instead of fiat there will be a market for crypto. Until that moment do not use fiat forex places that accepts crypto because it is neither nor situation there.
you could be mid-, or long-term invested in Bitcoin while daytrading Forex. why not use the Bitcoin which are "locked" anyways?