That's what I did in my house. 2 AP inside, 1 outside.
They were all AC AP PRO, now switching the 2 inside ones over to unifi 6 mesh. I have no plans of ever changing the outdoor one - well until it is not supported any more or breaks.
The outdoor AC PRO has been outside in direct Texas sunlight and rain (mounted on side of wall, no overhang) for over a year with no issues. I was curious how it would hold up - so far so good.
If you're doing wired then it's not technically "mesh".
I had one AP hooked up in mesh mode for a few months out in the pool house. It connects at 2.4Ghz so it definitely limits throughput. I just recently burried a cable from my network room to the building and hardwired it. Much better speeds out there now.
Outdoors I used to run a UAP-AC-M-PRO. The thing was great! HUGE range on it. It died on me though when earwigs took it over and then got crushed a week later when the tree I had it mounted to went down on top of it during huricane dorian.
i do something similiar old school. the main wired router i mentioned an older bufallo high power router with an outdoor 20db antennae mounted for outdoor coverage running a separate ssid. i can get this a block or two away. This only runs 2.4 G.
for indoor one of the asus rt-ac5300 "octopus" routers that works very well, and for the one corner of the house it doesnt reach a ex8000 extender..
All wifi routers are running dd-wrt except the extender.
i also forgot i hage a separate older netgear 7000 in garage on a separate subnet running just for the tesla as the tesla has issues with any network with steaming protocols..
i also have moca connecting upstairs to downstairs with switches on each end.. the house is about 3200 square feet
For indoors a ceiling mount works great w/the NanoHD and the other "flying saucer" APs (as my wife calls them). 
I have a NanoHD on the ceiling of my living room (center of the house) and it mostly disappears from view, we never notice it.
The coverage is just fantastic. I previously needed an eero Pro (base + two sats) to cover my house, and it did a great job. Probably still have it if eero did VLANs. I initially assumed I'd need two Unifi APs to replace the eero Pro. However, w/one NanoHD on the ceiling in the center of my house (~2000 sqft ranch) I get the same or better coverage. Covers inside and outside into the front and back yards. I've had 140mbps speeds on a chaise lounge outside the rear corner of my house. Completely pleased w/the Unifi AP.
Cool, unfortunately I'm not sure I'm going to be able to do ceiling mounts just because of how I'm going to be able/not able to run wires through the walls. Most likely I'll be mounting one on a wall on my first floor, one on my second floor and one outside (I have a bunch of cameras and an outdoor TV so I do a decent amount of video streaming outside!)
The Lite Wifi 6 APs are available
There are more than a few FW releasese from Ubiquiti that fall into that category. 
I was able to get 2 Wifi 6 Lite APs. I like them alot but they seem... "lite." The range is definitely lower than my Google Wifis. Indoors all is well, outside is another story. Going to need to come up with a solution for outdoors.
I'm sure part of my issue is that I haven't yet shut off the Google Wifi so I've got some interference going on, but still, not going to reach all my cameras.
How do you have them mounted? If I recall correctly the radio pattern is donut shaped for their APs, so ceiling mount is recommended. If you have them laying on their back, you may not have ideal coverage.
It might not be wifi 6, but these should work nicely for outdoor coverage: UniFi Mesh Access point – Ubiquiti Inc.
Unfortunately ceiling mount isn't possible as I can't get wires into the ceilings without removing drywall and I'm not looking to do that at the moment. I have one mounted on a wall, and the other on it's back on the floor. I'd love to get them on the ceiling, just not going to happen.
As far as outdoor, yeah those would work but I'm holding off for Wifi 6. My Google Wifi was working fine, I want to replace it with newer tech, not the same otherwise I'd just suffer with Google Big Brother for a while longer 
I wish they had a Wifi 6 version of that, the only outdoor option right now is this guy UniFi 6 Mesh – Ubiquiti Inc. which gets pricy. I need at least one, maybe two.
Lol the level some of you guys go is impressive. I would lose my mind trying to set some of this up. Yet alone trying to get stuff to talk to only the other stuff I say. I'd lose track.
Two ways it gets done, depends on who you are:
I'm pretty much in the second group...I end up getting things done, but pretty much purely through brute-force relentlessness and endlessly badgering smarter people for advice/instructions. 
I have gotten the notice that they are available twice now. Every time I get to the site, sold out... Share the love some!
So far I am really liking my UDM Pro. Plus I wrote a driver for it that turns our smartphones into presence sensors (like my previous router/ha could do). Once I get it refined some more I may post that project if there is interest. Just trying to decide what else I should do with the API that is actually relevant for HA purposes.
UniFi 6 Long-Range Access Point – Ubiquiti Inc. these guys were available for like 10 mins today. I managed to grab one, going to try putting it in my garage and hope it covers outdoors well enough!
Missed those also! My timing stinks.
So I started to reply to @danabw about the NanoHD and realized I actually have the FlexHD which I installed yesterday replacing an Orbi system. The Flex is situated in a closet on a shelf in the middle of our house on the main floor. Seems to be working well - no family complaints so far 
. I also have an AC-Pro that I might stick in the garage for giggles.
I did not go the UDM Pro route as I already have a great firewall set up running Opnsense. I do have an 8 & 24 port Unifi Switch and a cloud key as well.
I'm sure my wife would prefer if I had your timing because then UPS wouldn't keep coming with more "wifi flying saucers" that deplete our bank account
Only device I've had issues with on their wifi has been my Ecobee, it seems to dislike something and lose the connection, I'm still messing with settings to try to get it working
Strange.
I just installed a Ubiquiti system with a UDM and multiple Nano's.
The first thing that the client said "What are those flying saucers on the ceiling?"
Refer them to a few seasons of "Lost in Space" and they will decide they love them!
Seriously...they disappear from view almost immediately. I never think of mine or see it any more. Can't remember the last time I looked at it consciously.
OK, no jokes about my conscious being particularly weak, @erktrek.
Download the Hubitat app
