Well, if you buy fifa points from a different account, it wont give you points on your main account.
You could open packs with the points on the alt account and buy players for max price put up on transfermarket from your main account.
Just put some shitty bronze player up for 10 k buy now, find the player from the alt and buy, easy easy.
Honestly, don't buy accounts with fifa points on it, just buy points or coins on your main account. Too much of a hassle and you loose coins on the EA 5% tax...
Any other questions just hmu