Oh I have concerns on the 2.4ghz range actually. I thought ax86u is still better option?
Why do you have concerns on the 2.4GHz range? Are you relying on 2.4GHz for your main devices like mobile phones, tablets and desktop/laptop? If that is the case, the right solution is to use a mesh solution and not to rely on 2.4GHz in Singapore. 2.4GHz is too congested in Singapore.
BTW, it is better to use 20MHz channel bandwidth in Singapore and not 20MHz/40MHz.
But if your main concern is IoT and legacy 2.4GHz devices, then it is indeed good to keep using RT-AX86U.
I will recommend to keep the RT-BE92U for the main devices and then use RT-AX86U to serve 2.4GHz device. But it is up to you. It is fine to keep using RT-AX86U if you have no issues with it.
I am using RT-AX86U for my Singtel 5Gbps plan to serve legacy 2.4GHz device. Then I have TP-Link Archer BE805 (or Asus TUF-BE6500) to serve the main clients.