My favorite is stainless hangers in tanks, I have a narrow stainless tank that holds about 5 hangers and doesn't require much chem. When I don't do it that way, I process in trays or occasionally in a Jobo with the sheet reel.
If I were starting from scratch I'd go either with the slosher tray or a Combi Plan tank. On ebay there are also the inserts that go into Patterson tanks, which look promising.

Yes, with trays and deep tanks, you work in the dark, no safelights. I find it restful

How many at a time depends on your skills. I know folks who do 20 sheets at a time, my limit is about 10.