PVE multiboxing is much better in pandaland than it was during cata, but it isn't easy enough to mb raids so once you clear the heroics you won't have much to do unless you really love lfr. And LFR probably won't love you, so pick discreetish names. The game is also geared more towards doing a lot of dailies than chain running heroics, so that's much more unpleasant unless you like dailies (and if you do what is wrong with you?). I personally found Cata content to be very very painful, even multiple patches in, with the stupid hard hitting trash of ZA especially burned into my mind. Pandaland is much more fun.

Macros and addons yes, but you don't have the ,, ,,,,,,, click macros so people tend to use several spammable or sequence macros instead. You'll find plenty in the macro forum, or just ask about your specific classes.

Isboxer is the standard software for people on these forums but we support the others as well (with the exception of pwnboxer, although no longer banned from discussion, I don't think we have enough people using it here for this to be primary support). At this point the forums are owned by Lax (dev of isboxer) but other software is supported and there are people that help with and use others (HKN especially).