You can probably get away with 60mm/2.35".
And the easiest 1x setup is sram. I'm running x7.2 RD and gx 10-speed shifter on one of my bikes. Totally painless to setup.
Be sure to get a NW-chainring though or get ready to but your chain back on all the time.
Yeah, it’s 1x (after a lot of tears and boiling, long story). Get a dynamo or don’t bother, and yes the aforementioned knobbly tyres.