Another good resource is the most revised general rules, as opposed to the forum-specific rules:
(You of course may have already reviewed them, since you mentioned the “more rules” but juuuuust in case. NOTE - think this is the most recently discussed version (with feedback), but see also the full TOS)
I also echo @kenobi_65’s suggestions for least charged forums to follow. One additional is probably IMHO (like it sounds) which is a step-up in seriousness from MPSIMS in intensity but a step down from the more charged Great Debates.
But it is absolutely more debate-y - so, in keeping to your wishes and Kenobi’s completely valid recommendations, it might be the next expansion after getting your feet wet in the forums they advise on.