XR500 with multiple EX7700 or should I use something different?

I'm back with an update.

I purchased a second EX7700 and it was extremely problematic to say the least.

The browser link for the extender is mywifiext.local, which wants to resolve to only a single dynamically assigned IP. So I set my first extender to use a manually assigned IP. This took a little bit of fiddling to get working, but eventually I was able to log in to the admin panel via a browser by going directly to the IP and logging in.

So I started the setup of the second one and that's where the problems started. After going through the setup I was not able to get to the new extender via the admin panel in the browser using mywifiext.local. I would get a challenge response and every time I tried to log in, either with the password I set or the default password, it just wouldn't log in. In the app, I could see both extenders in my network map, but if I tried to switch to either one in the app I would be given a login screen and regardless of whether I used the password for the 1st extender, or the password for the 2nd, or the default password it would say I couldn't log in. So I had no way to actually access the second extender to manage it.

The network itself was not working well. The mesh system didn't appear to be working great. I was getting dropped all over the house and the speed wasn't great. The locations were far enough apart but they still didn't seem to be handing off to each other gracefully. The second extender actually made the whole experience worse than with just the single extender. So after much fiddling I gave up.

I returned the second extender and purchased the Orbi 970 system, which costs a small fortune, but is giving me basically gigabit throughout every corner the house and will set me up for (hopefully) years to come.

So, anyone thinking of doing this... though maybe it technically "can be done" it likely isn't all that viable unless you're a rockstar network admin.