I think you can go either way (replace 74 with 76 or replace 86 with 81). I have not felt the Quads are less beneficial in high wind than they are in low wind.
But your message indicates that you seem to like riding the EVO the most. Then it will make sense to replace the A86. The Q81 will certainly handle light wind at least as well as the A86 by virtue of more fins (upwind etc) and more surface area, apart from when you are really standing absolutely still when it comes a point when volume counts.
And I think you can take the Q81 out in 4.2 weather too. I friend of mine who is your weight used my Q81 last time we had 4.2 winds and thought it handled super well.