Answering my own questions 1 day later:

Re: Blowing Bubbles - I believe the author's intention on Blowing Bubbles (spread > stack) is to have melees take the northmost and southmost initial safe tiles, (see the above raid plan I made). Depending on the exaflare pattern, these northmost and southmost safe tiles might be in either corner. So on some pulls the tank, for instance, would be NW if that's where the northmost safe tile is. On other pulls, they could be NE. This does make sense for melee uptime as melee players will then circle back through the boss's hitbox rather than along the edge of the arena. That said, some early PF groups are just ignoring this part of the pastebin and doing static corners (i.e. tank always NW).

Re: adds priority - As the author noted above the day 1 explanations, they're not updated, hence why the prios are different. Again some PFs do it flipped but easiest at this point just to stick to what's at the top of the pastebin.