I always do everything HC 2 pass by overriding the AVStoDVD settings. Yeah, it takes some extra time for probably only a marginal improvement. But I figure hey, if it's worth doing, it's worth trying to achieve optimal quality.
To this day, I've never messed around with QuEnc. I don't have anything against it, per se. It's just that a HC encode looks so darn good I've stuck with it by habit.
Regarding luminace gain (LUMGAIN), I no longer use it. Some while ago I was using LUMGAIN 2 on a DVD source with lots of CGI content and HCenc locked up. After trying multiple times with the same failure, I removed LUMGAIN and was able to complete the encode. Mind you, this was a couple HC versions ago.
Bug or isolated incident? No idea, but I haven't used LUMGAIN since so as to avoid any possible issues.