So I'm guessing, to do the tail the only thing I really should decide on is elec. or manual trim....that's done, electric. Then Vans or Ray Allen? I'm assuming it's much easier to do electric trim while the elevator and stab are being built than after...
The electric trim Vans supplies with the tail kit is a Ray Allen motor and hardware.
Or thing you may like to consider early in the piece is if you're going to paint the aircraft or go with polished aluminium. If the latter, it will probably be easier if you polish each elevator separately, the VS separate to the rudder, etc.
While I agree the capability in avionics changes rapidly, I settled on Dynon products long before I'd even bought the kit. I'd watched their development since the first D10 and decided that they were the best for me. Pick a supplier that you like and go from there. It is easier to install autopilot hardware while things are apart, but in saying that the (Dynon) servos can be installed easily at a later date.
Think about what lights you want - even DIY if you want - and run a couple of extra wires in your loom for contingencies. It is easier to run wires while things are apart than trying to snake them through an already-built assembly, even the QB fuselage and wings can introduce some challenges there.
Don't decide on engines and props till much later. I was sure I was going to get a new donk from Aerosport, but found an alright deal on a 76-series Lycoming down the road so bought that instead. Which in turn requires modification to the engine mount I've already got from Vans - no big deal, but an example of how changing decisions halfway through can have more ramifications than just what you see in front of you.
Finally, don't plan on doing anything quickly with your build. Everything takes longer than you think it will, so think accordingly.