One further comment about Asus firmware being quirky or having issues. It is likely that for the average user, the Asus firmware will operate as expected. It tends to be power users, or those who tinker with the settings, or those with fringe use cases/hardware/ISP's who find the bugs and issues with the firmware. Once I understood how the 3006.102.x firmware's Guest Network Pro works, and it's limitations, I was able to configure it successfully for my basic no frills use case.
The main problem with the Guest Network Pro and certain other 3006 firmware features is the absolute lack of detailed information on the feature(s) from Asus. Instead it's left to the user to stumble their way through the feature/firmware and try to make it work for their use case. One of the biggest issues was the Guest Network Pro option "Use same subnet as main network", if you want your Guest Network isolated from main LAN, that option generally needs to be disabled (turned off). The problem is some of the Guest Network profiles default to having the "Use same subnet as main network" option enabled. Users who don't understand that option, and don't disable it, are then left wondering why their Guest Network Pro profile (like IoT) is not isolated from main LAN. Another major issue was the lack of information from Asus about what features or options in 3006 firmware do not flow down to 3004 AiMesh nodes. Instead users are forced to experiment to see what works and what doesn't in their use case. So much confusion and frustration we see posted here about 3006 firmware could have been alleviated by Asus simply having detailed information available about the 3006 firmware features and that firmware's limitations when using AiMesh nodes on earlier firmware tracks.