1. No, any class that is not active (assuming more classes may be available in the future), i.e. not your primary or your secondary class has no effect on your toon at all.
2. The same as above.
You can be R/W or R/S, there is no inbetween or sharing of skills.
The only thing that you do have to share is your Rogue TP pool (e.g. your Tp invested in your R/S elite skills are MIA for your R/W) and your action bar setup. Probably it is best to keep all your R/W elites and Warrior general skills in one bar, to be swapped with another easily for R/S and Scout general.