Best alternator amp for my setup,And one wire or not?

I don't think that you can have too much ampacity. You can spend more than you needed to. And you can seemingly get a lot for not much. Can have: Quality <> Price <> Amps; Pick any two.

Alts are output rated at their best RPM, which you won't always be running at. Was it me I'd look at how much current can everything in the car draw total when all turned on at once, add some margin (20%-30% at least) for safety and so that even with everything turned on that there is enough left over to slowly charge the battery, and buy that.

Which one to buy really depends on your abilities. If you can create brackets from scratch, then buy what ever you want. If you're needing to use a pre-made set of brackets then you're limited to what those are designed to work with.