What have some of you found works best?
There are as many answers to this as there are people who use subs.What's "best" for me might not work for YOU at all.YOU have to experiment and put it where it sounds best to YOU. YOU are the one that is hearing it.YOU are the one that has to live with it.Notice the emphasis on YOU?Start out using placements suggested in the manual and work from there.Good luck.
Finally, do subs with automatic room equalization functions render placement a relative non-issue?
IMHO,no.