On old wireless this was possible but those drivers were developed in-house so there was a lot more control.
With wifi-qcom drivers (vendor drivers with some in-house adjustments) this is not possible anymore.
AX means everything from 802.11b/g/n/ax
If your laptop only wants to use G, that's what it will get.
PS must be a REALLY old laptop then ?
Set the Security for your needs and roaming /interface wifi security name=<sec_name> ...
The channel config /interface wifi channel add disabled=no name=<channels_name> skip-dfs-channels=10min-cac
for roaming /interface wifi steering add disabled=no name=<stearing_name> rrm=yes wnm=yes
Manager for wifi interfaces
5a. for the device where CAPsMAN is /interface/wifi/set wifi1,wifi2 configuration.manager=capsman-or-local
5b. for the CAP /interface/wifi/set wifi1,wifi2 configuration.manager=capsman
Don't forget to provision the CAP, and on the CAP enable the CAP setting
If you want to see what channels / band are used per wifi interface on the CAPsMAN device: /interface wifi monitor <wifi_name> without-paging once
If you use Tab after monitor you get all wifi interface names