If you flash CM12.1 you will have to flash the last nightly from April that I posted a few months ago. The same Quark queue is used for CM13 and all the CM12.1 ROMs got pushed out, as far as I know. But somebody asked for it and I posted it.
I always flash SuperSu. Custom kernel is not necessary. I like BHB27 kernel, but my wife's phone doesn't. Don't ask me why. Maybe because hers was Mexico I flashed to India before flashing CM custom ROM, and there's some remnant of something somewhere. But mine was Puerto RIco and I flashed India before flashing to CM. I don't know. Anyway to keep both our phones on the same support level, I had to remove BHB27 kernel from her phone as it would randomly reboot and lose her wallpaper and stuff like that, so I so removed it from my phone as well.
One ROM I would suggest you try is the
Resurrection Remix 5.1.1
RR is based on CM, but has more options. Seems like some have ditched Marshmallow to go retro, back to a simpler, faster Lolllipop ROM.
[ROM][All Quark][5.1.1]Resurrection Remix 5.5.9 [Optimized / O3 / GRAPHITE / KRAIT]
http://forum.xda-developers.com/moto-maxx/development/rom-resurrection-remix-5-5-5-t3197643
When I do go Marshmallow I would probably go Bliss or Resurrection Remix.
