Me personally- i would look at the wheels and go from thwre. So many of your questions can be decided, or at least narrowed down, based on if you want to keep your current wheelset.

If you want to keep your current wheelset, then no need (or option) for more gears. You could then focus on new 7sp shifters and decide if you want different derailleurs or not.

If you want a new wheelset, then itd make sense to get more gears and components to match. I am building up a 90s mtb right now and have been getting great condition Deore LX and XT components on ebay for cheaper than new Deore or Alivio components.
I have Alivio 9sp trigger shifters, got em again off ebay for something like $18.

Trigger shifters and butterfly bars would be my setup. I had a bike last summer with butterflys and they are very versatile.