Heard from my friend, he had nightmare with AX50 within 1st year of purchase. Main issue is overheat problem and ended up he bought AX20. So far AX20 seems to be good according to him.
Not sure, If TP-Link already fix this in newer models. But, I believe AX50 is still in v1 according to their website.
If you have budget to get RT-AX3000, why not consider TP-Link AX73 (AX5400) model? Currently on pre-order with ETA from 8th Feb and their introduce price are so attractive which is RM 399 (with free Tapo P100) or RM448 (with TX50E).
You can look for TP-Link official site at Shopee or Lazada.

Suggest you to buy 2 units RT-AX55.
having promotion right now: https://shopee.com.my/Asus-RT-AX55-AX1800-W...0984.4161367975

the old RT-AC68U can upgrade to latest firmware and get it support on AiMesh.

Yup. From the LAN port of the NETIS to the WAN port of the new router you bought.

Yes, AX having more band that less unlikely having overlap with other.
Its sure will improve a lot from AC1200. Somemore you able add RE505X if need for double storey

You can refer my previous comment here, https://forum.lowyat.net/index.php?act=ST&f...post&p=99927504
I used to own both but decided to keep ax73 and sell ax56u. In short, for the same price range, tplink gives better performance but asus give better software/feature.
I think you got a bad unit? Try to reset and reconfigure again, if the same issue still persist just send it for warranty. I've faced one time blackout while using this ax73, and the router bootup itself normally after the electricity restored. Tested to switch off/on using the physical button, still didn't face the ssid rename as you mention. Below is my ping result to the same ip as per your screenshot using pc connected via lan, fyi I'm on time fibre not unifi ya.