Can anyone help me.

I bought this Granny Smith apple tree recently on M26 rootstock. I want to keep it in a patio pot for now as we should be moving at some point in the future.

My problem is the Y shape in its structure. Should I keep this shape and try to fan train it? Should I choose one of the branches to keep as a leader or take them both off? There are also several other thinner branches below the 'crotch' (I think its called), should I keep these?

The garden centre seems to have pruned back a branch between the two larger branches (that I would have used as the leader because it looks central, do you think they were starting to fan train it?

Anyone who has the time to let me know what they would do to get the best harvest out of it would be great.

I don't know the age of the tree, sorry?

Jamie