Yes one can do both and grading is simply the buying and selling of financial assets  which might include foreign exchange (Forex) stock, gold, cryptocurrency and lot more of them and I believe  you're referring  to trading g them online when then .amen it digital assets.
Both Forex  and cryptocurrency  assist that can be traded and depending  on how good and conversant one might be with each assets determines how much profits one could get and speak  of such asset.
Both  trading are good and yes both can be traded by one person rather than  switching  sides.