I just use thin CA for hardening the threads and retap, as far as regular wood glue joints are concerned, the tight fit is what transfers the load, A fillet is used to give the bond a little more base and support, it's hard to say which joints need a fillet and which ones don't, but in general, every fillet is adding weight to the plane. I see alot of people do fillet beads everywhere, it's a big waste of money to me and just unneccessary weight added. But that's my own personal opinnion. The structure as a whole is what gives it the striength, not the glue sticking it together.