Applepay and wallet

What’s the difference between applepay and wallet?

I’ve got 4 bank cards on my phone where if I double click the power button I can pay at the shops.

If I go to settings on my phone and select payment and shipping my methods are applepay (4 cards) and two of my cards. I don’t understand why?

Also how do you control which bank account things are paid from? My icloud payment goes out and of one account, Apple Music out of another. One is my business account the other my bills account… neither of which I would have selected if given the option. I want to change both payments to a different account.

There’s far too many screens and options.