My IOT network is only 2.4ghz as all these devices only work on 2.4ghzMy GT-BE98 Pro network would experience that lag a really long time ago, maybe end of 2023 when I first got it.
I got this image from https://www.asus.com/support/faq/1053665/#a1
View attachment 67014
Also note "Use same subnet as main network" is probably a good idea/enabled by default.
I have few IoTs, and they connect to my main network....