I've cut apart and reassembled 100s of cues. I've seen some pretty interesting A joints and a couple that challenge everything I think I know about cue construction. Conclusion? There is no secret sauce. It does have influence on the overall feel of a cue but, not as much as I once thought.
Finishing over the wrap is finicky. The linen can discolor and/or be blotchy. It been several years since I messed with Solerez products but the grain filler should work. There's still more to it than installing the wrap and brushing on the sealer.
I've seen jumpers built built in every configuration. They all work and there is not a one-size-fits-all. The best advice I can give in building any cue is this; build yourself a few. One heavy, one light. One maple, one Purpleheart....etc. Figure out which one suits you best. Let others test...