Steam is the most used platform to bind your games to in gforce now so i would be supprised if there was an issue. However I will not say you wont get trouble, I just wanna holler out to everyone who use gforce now to come over to answer if there is problems with in game purchase with apex on steam through gforce now :D
I hope you get an answer for this, I tested so many things and found gforce now to be the best cheap platform to do mnk if youre on console so kudos to get a good sticky or something on this one, or atleast get the information into one of the stickies for the forum.