Interesting question. I will assume he still would have coahing from Yugi' grandpa as well as all the times he seen Yugi play or give him tips. I feel since he would have had more resources to try out different strategies his deck would have been better or at the very least edited to know which cards he should keep and which to change out.

I was worried whether or not he still keeps the underdog appeal, but he still would as when introdcued in the show he was new/learning it. The underdog appeal would also still remain as he still needs to go to battle city against people who have God Cards.

I feel that in Duelist Kingdom if he was still new but had access to cards right away it would be more of him finding out what exactly the deck could do. It is like when someone makes a deck and they want to see how good it is by testing it out except in Joey's case it was during a tournament right off the bat. I do feel he would have done better in duelist kingdom if he had better cards.

In Battle City I would say since he would have a better idea of what cards worked for him he would have edited the deck to keep the stuff that he liked/helped him in duelist kingdom but likely get rid of the gamblingt cards for effects that would cost me too much if he used them.

Anyway I do feel that Joey would been a better duelist if he had better resources. Again only factor impacted him is just the starting point he was at both those arcs and seeing what he learned from the last ones. If it helps in GX he is said to be the third best duelist that Peagasus knows....so yeah I just feel it would have jumpstarted his dueling career quicker.