Raleigh Dyna-Tech 700 build

Newbie question 1: if I go with a 126mm hub can I still fit a 9speed cassette?

You certainly can. I run a 7speed with a spacer on one bike and a 9 speed cassette on my raleigh clubman. I'm going to try a 10 speed cassette on my bob jackson build also spaced at 126mm.

Good luck with the build.

Party on. It's all a bit confusing I'll be honest but I'm sure it'll come together. Probably with a bit of money down the drain but it's all good fun.