Isolate your IoT devices from the Intranet (aka your local internal network - LAN) or from the Internet (aka the WAN)?My current setup does include "several" IOT devices that I keep reading should be placed on a VLAN to isolate them from the internet.
Generally for isolating IoT devices from the LAN/Intranet one can use the WiFi Guest Network feature of existing Asus routers to accomplish that task. For blocking Internet access that typically involves either using Parental Controls > Time Scheduling, or if using Asus-Merlin firmware using YazFi WiFi addon, or using scripting to block clients from accessing the Internet.
Currently the Guest Network Pro feature of the 3.0.0.6.102_x firmware on the AX Pro series and certain newer Asus routers is a mixed bag. Some features do not work as expected, or the features have quirks or issues. Use the forum search to find various other discussions on Guest Network Pro issues when trying to isolate WiFi guest clients from the Internet.