Just FYI, your Asus router has Trend Micro security...Apple recently banned Trend Micro from their App Store (for Macs) because it got caught sending browsing history and other info to China servers:
Apple takes down Trend Micro Mac apps that collected, stored user data | Ars Technica
Not a big deal, but for me personally, i stay away from anything Trend Micro makes or associate with.
Your experience with mesh...makes me glad that i did not spend money on mesh!
I am using Apple Extreme routers from 2013...3 of them total (1 base connected to Xfinity modem, and 2 satellites are connected to wall via Ethernet).
My iMac Pro is connected by Ethernet straight to the base Apple router. I am getting easily 850+ in Speedtest.net (and Xfinity speed test). And this with the 2 satellites connected (via Ethernet to wall outlet).
But my setup is not mesh. It is just 3 Apple Extreme connected via hardwire. Same network name and password. The 2 satellites are in "Bridge mode".
So far, i love my setup. The transition from router to router may not be as smooth as mesh, but i have NOT noticed any issue in the transition...not noticeable by my or my kids.
As for modem, i used to buy my own instead of renting from Comcast/Xfinity. Saves $120 every year. Except that when i had any issue with connection at the house, they ALWAYS blame my 3rd party modem (Zoom i think). It got tiring dealing with that because it always comes back to that. And at times, it was the 3rd party modem that i bought that was the problem...but it became a customer service nightmare everytime i called. Comcast/Xfinity always use it as scapegoat! So, now, i pay $120 per year to rent Comcast modem. That way, much less headaches...and i must admit less issue too.