In most good routers/APs (Unifi, OpenWrt, etc.) WiFi client isolation is something that is just a simple toggle (don't remember if it's on by default) and placing an SSID on a separate VLAN is also easy.

Some more consumer-oriented router/APs like Fritz!Box support a guest network that uses WiFi client isolation and internally uses a VLAN that is separate from the main network (though due to being non-pro end-user focus, you cannot set up your own VLANs or additional SSIDs).