The ARF airplane box often has engine and prop recommendation printed on the box. The engine usually has a prop chart in the manual. Once you have chosen a specific airplane and engine, post the info on RCU and ask for suggestions. Be prepared for WIDELY varying opinions though. If you've already chosen a club, go there and ask the instructors for advice on plane/engine/prop/etc.

The club is also the place to get the "mode 1 vs mode 2" question answered. It matters more what your instructor uses and knows than 'what is most popular.'