Thanks Xiaofan. I forgot to mentioned, I do also have a ceiling mounted UniFi nanoHD AP. Seems also not to be using as AX88u can cover my whole house.You can carry out the test. I tend to think HB611-SGST will have worse wireless coverage than your RT-AX88U.
My test shows that TP-Link HB710 has worse coverage than my Asus RT-AX86U. Archer BE805 has same or better coverage compared to RT-AX86U.
You may want to keep your RT-AX88U if you encounter compatibility issues or wireless coverage issues with your HB611-SGST. I keep my Asus RT-AX86U to use with legacy 2.4GHz devices.
If you want to upgrade, then Archer BE805 is probably one of the most cost effective model (less than S$300, dumpled by M1 users) to mesh with your HB611-SGST.
Will test it on HB611 and see if the coverage is good or worse.
If I’m not going on using mesh system, Will Archer BE805 cover the whole house? Haha