@Baseball_jp Welcome to the forum!

It's a little difficult to give you an answer to your issue of dropping WiFi client devices given the info in your post.

First of all do you have any 6 GHz (aka WiFi 6E or 7) devices?

Did you know that 6 GHz has less range than 5 GHz which has less range than 2.4 GHz?  It could be that the nodes are too far for 6 GHz backhaul/connection between/among them.

Wired backhaul would help either system, whichever you end up choosing.  I understand that it seems either you keep the XE75 or return and wire the X60.  But I'm not sure which I'd recommend to you, I don't have enough information.  I assume your preference is not to wire as you've already bought the XE75...

  @jzchen 

Thanks for the quick reply.

Yeah, nothing seems to be using the 6GHz band. I did read that 6ghz band has a shorter range. I just think it was a bad decision by TP. Link to eliminate the option in the software to dedicate one band to communication between the nodes. I think a recent firmware update fixed the device connection/ dropping issues, but I'm continuing to monitor it. 

I would prefer to wire the devices but running wire behind the walls is going to be difficult so I'm putting it off as long as I can. If the nodes are communicating quickly with one another and I'm getting optimal speeds in every room then there would be no reason to do it. Since nothing is using the 6ghz band. I'm not sure the new system is any better than the old one. I have been experiencing fewer drops, but as I said, it may be attributable to a recent firmware update then the tri-band router. 

I have about 55 devices connected to the network. The x60 said it could handle 150 devices, and the xe75 says it can handle 200 devices.  I'm probably not going to return the xe75 but with nothing using the third band, it probably wasn't necessary for me to upgrade.

  @Baseball_jp That's a lot of devices, (at least for me.  I avoided WiFi as long as I could, and have wires around the house which I've been told "is ugly").

Would you mind sharing which 6E or WiFi 7 devices are not connecting via 6 GHz?  They should, especially if they are near to a node.  There are TP-Link staff that roam here who can facilitate with engineers to fix this...

  @jzchen 

Not sure which ones are and aren't. I googled if a pixel 9a is compatible and it says it is. It does connect to 5Ghz but so far never to 6ghz. I've only had the new system for a couple of weeks so maybe it will in the future

  @Baseball_jp I just realized there is updated firmware available.  It warns irreversible but I still think it's a good idea to update all the nodes.  Please update and check whether the system is running better...