I'm going to install hardwood strips and stair nose where carpet was. Couple questions:
1. Do I need to glue and nail all of them or are nails alone good enough for everything but the nose?
2. Some folks have mentioned putting a 30 degree backcut on the ends of the strip that touch the wall. Why is this done?

Thanks

You are right there with glue in hand, may as well glue the strips while you are at it. Dont forget that these steps will take a lot more wear than the floor will. The 30 degree backcut is probably being recommended to give a tighter fit along the drywall, which is usually mudded out with no great amount of accuracy.

I use urethane glue, in a caulking tube, and brad nails.

Cutting a bevel on the ends, is for sheetrock mostly, but some guys cut a tad long and then sand to get the right fit, against wood stringers. Less wood touching the stringer, means less chance of a squeak.

Assemble the stair dry without glue or nails. Once on and tight, shoot brad nails along the back board/s as close to the edge, near the next riser up.
Disassemble the remaining boards and stairnose. Then lift the edge ever so slightly and stick the nozzle of your urethane adhesive under it and squeeze the trigger. Push that board down seating it and then pop brad nails at an angle into the top of the tongue, to blind nail it.
Take the next row and apply beads of glue in rows or as an exaggerated serpentine down the back of the board. Place it and get it tight, then blind nail it with the brad nailer.

Do the same with the stairnose, with the glue, but now your going to need to top nail it. I like two brads in each side, then depending how wide. either right down the middle, or two to make it symmetrical. no more than a foot between stairnose nails.

The riser the same way, only I don't top nail the bottm sitting down on the tread piece. I glue it and then blind nail.