I like keeping IoT devices separate; security for IoT devices is notoriously weak.
Also, when using wireless, many IoT devices do not store WiFi credentials securely (think plain text on the file system) so if they are easily compromised, so is your WiFi network (obviously only an issue if your attacker is targeting you specifically and is in range of your AP.)
Running multiple routers/firewalls/access points requires some above average knowledge of networking though so it’s not for everyone. Most consumer products are designed with the assumption that everything is on One Big Home Network, so not everything will be as seamless as promised on the box if you go this route.
One of the best things I have done is move from a standard router to running pfSense in a virtual machine that has 3 network cards. 1 - for WAN, 1 - for LAN and 1-for IOT. You can also buy a standalone appliance from pfSense. I now use my old router as a wifi access point only