Folks, I'm probably overthinking this, and, I really prefer making rational decisions as compared to a shot in the dark.

Question 1:  Every one of the TP-Link ceiling mount access points indicates that they can also be mounted on the wall.  But at what coverage cost?  I've got 3 offices, the largest of which is 23' x 20' and I plan on hanging EAP610's on the wall in these offices, figuring that they are small enough that any attenuation because of being mounted on the wall won't matter.  The walls in these offices are 8 inch thick concrete.  There will rarely be more than 4 or 5 devices connected in any office.  Is my reasoning reasonable here?

I have two large rooms with high ceilings that I cannot reach.  One is the fellowship hall, about 40' x 30', while the sanctuary is about 60' x 40' ft.  When in use, these rooms may have as many as 70 or 80 people in them.  Consequently, I am thinking about using an EAP660 HD device (more in Question 2 below).

For the fellowship hall, I will be mounting the AP where the red arrow is (white dot on wall is a battery operated smoked alarm).  Will the AP operate satisfactorily if wall mounted as shown?

For the sanctuary, I will mount the AP in the space where the AV room overlooks the sanctuary (red arrow).  If more AP's are required, I would put one near each speaker to the left and right.  Again, this will be wall mounted.

Question 2:  The general question is, "Do TP-Link ceiling mounts work as well on the wall?  Because TP-Link supplies mounting kits for both places and this suggests that the signal is sufficiently omnidirectional so that the mounting doesn't matter.  True?

And then comes the question of, "What device?"  I know that the speeds and devices are completely theoretical and don't reflect the real world.Do I really need the EAP660 HD or will the EAP620 HD work just as well?  I have one device mounted on a hallway ceiling that serves 6 rooms, three on a side, with about a 30 foot radius (and all are sheetrock walls).  Will the EAP610 work here or should I spring for the EAP620 HD, since these rooms could have as many as 15 people in them from time to time?

This is a church in an impoverished area of town so it does a lot of foodbank work and other activities.  This whole installation is a volunteer effort, and while I've elected to go with AX AP's because this install isn't going to happen again, I'm still trying to be cost conscious.

Overall, I find the whole bunch of product offerings rather confusing and overlapping.  Any thoughts on differentiators would be greatly appreciated.

TIA