b) Will the above setup give me RAF bonus if I play with characters on 1,2,X,Y,Z grouped?

c) Could I achieve B with just 2 new accounts?

Yes to B. That's exactly what I did as I had 2 accounts before RAF started (1 RAF'd X, 2 RAF'd Y and X RAF'd Z - for me). Ticks suggestion is probably better for you though.

No to C. I don't see how you could do this without linking a third account unless your current accounts are already linked. Actually, I am not ever sure exactly what you mean.....