I used to use multiple RT-AC86U ASUS routers before moving to a ubiquity setup, but the Merlin firmware was the way to go when I used them. I think ASUS was one of the first to support mesh with their consumer routers and you could mix and match various routers together, but the Merlin firmware was originally not allowed to implement mesh (believe this has now changed), so I was forced to stick with the ASUS official firmware to make it all work. Eventually ran into a myriad of issues due to the number of concurrently connected devices as I added a ton of smart home devices to my network and decided to look for a solution where I could have more control over segmenting devices on the network.