Tsukuba is technical, has every type of corner and acceleration zone, and is short and easily repeatable without wasting too much time. Works great for cars up to Gr4 speed.
Faster than that, for some reason I gravitated toward Alsace Village. I don't know, I just got really good at the track and it's super repeatable for me. Only problem is it's long so it takes a while to reset after a mistake. It's a really thorough test of anything Gr4 and faster. Lots of trail braking and braking while turning to test stability and braking balance.