So you are telling me to forget about what device maker says (actually, lies) ...
The way I see it is you're asking a question, you get valid answers but your argumenting on each answer you get.
Then why ask the question if you think you know it better ?
Where is the lie ?
You are not interpreting the numbers correctly.
AX2 needs higher transmission power because it does not have those external antennas.
Again, look at the reception side. Which device do you think has the best sensitivity ?
You still did not answer that question.
If I follow your logic, there would be no need for antennas on base stations for cell phones either. Just stick a couple of square cm's of whatever on a building and it should work.
Then why are cell providers installing all those antennas all over the world ? They must be stupid then ?
External antennas have a purpose. They increase transmission and reception range.
Internal antennas provide a more equal distribution of range (ball shaped). Perfect for a room.
External antennas can provide more doughnut shaped distribution, better for longer range.
Broadly speaking AX2 and AX3 are the same internally. Range wise AX3 is the best of both.
Since you mention this setup will be for an apartment (therefor I assume 1 floor):
If you only need reception within a room, go for AX2. Signal may pass one wall maybe two (depends on material the wall is build with) but I wouldn't expect too much from it.
If you need to go beyond a room, use AX3. Or put an AX2 in each and every single space.
My guess: 2 AX3's placed diagonally and you can cover the whole apartment.
Again:
I have two AC3's (same antenna concept as AX3) and they cover a HOUSE (1 floor is 110 sq meters, there is a full basement, 2 floors and an attic. All walls are brick and floors are concrete)
The AX3 I am toying with now goes from my office on the second floor within the range of the AC3 diagonally placed on the other side in the living room on the first floor.
Your choice.
And forget about meshing using wireless. Use wires for connecting all your APs and when the client hops from one AP to the other, there will be a slight delay.
But AX3 will help your client staying connected for as long as possible to the same AP.
And now I stop responding here.