depends how fast Wifi has to be for your clients, is 20 or 40MHz bandwith limiting you somehow? If yes better use 100-112 with 80MHz.
And are there other networks around using the channels you want to use? Too much interferences will slow down more than you get with more bandwith.
Do you really need the second higher band at all?
If you use Aimesh it will be used only as backhaul with no clients on it even if you have LAN-backhaul, so it is unused anyway.
20 or 40MHz is not limiting any clients that I'm aware of. Now I'm using 5GHz-2 on 80MHz and channel 112 static.
I choosed the channels avoiding other networks around, in particular for 2,4Ghz WiFi.
And you hit it, 5Ghz-2 is used as backhaul.
My Network is:
1) Modem for FTTC Connection with RT-AC5300 in DMZ, I don't use this modem for anything except connection
2) Asus RT-AC5300 as main router, AiMesh Router
3) Asus RT-AC68U AiMesh node
4) Asus RT-AC56U as media bridge connected to one of the two 5GHz WiFi, I don't remember if it's the same wifi of the backhaul, do you suggest to don't use 5GHz-2 for the media bridge connection?
5) Asus DSL-N55U Annex A connected to one of the ethernet port of RT-AC56U and configured as AP, generating wifis on different channels than RT-AC5300, should DSL-N55U be configured with WDS for better result instead of using the ethernet connection to RT-AC56U?
I see WDS got security issue, open and wep are bad to be used