I’m using black walnut for the sides and cherry for the top/back. The walnut was sourced from a fallen tree on my property a few years back (the tree was small though so if anything goes wrong I won’t have enough have may have to substitute something else). The cherry from a tree my grandpa had cut just before he died. I’m currently cutting up an ash tree that I hope to turn into the neck.
As for bracing, I’m not sure, but probably whatever plans I found online show.
The above is of course the plan, and subject to change as I discover something in it will/cannot work.
Rates are not high. 20 years ago they were higher yet - and people are cheering the historically low rates. However if you don’t remember 20 years ago it is easy to think they are high now when in fact they are probably closer to normal.