A little help understanding how I could segregate smart devices on my lan

Background on my network:

I have multiple access points 3x Netgear R7800 and 1x Linksys ACM3200. I run one ssid for 5G and 2G with a wired backbone, dummy ap setup - one dhcp server, different channels to give a ‘whole home’ coverage. This makes for a very crowded wifi area. I do run a guest wifi which is a different SSID, which clashes on channels, but that’s not on all the time. should I be worried about channel interference from other ssids?

If I wanted to segregate my smart devices(all wifi based) via vlans. Is my only option another SSID? I’m trying to limit the already crowded wifi.

My house isn’t that big but we rely on wifi calling which needs a solid wifi signal. My devices don’t struggle to hand over between APs.

Thank you experts!!

Unless you want to install dedicated APs for this, yes. As long as all of your APs use a wired backhaul this is rather easy, with wireless backhauls you'd need to investigate (GRE-) tunnels, as WLAN itself has no concept of VLANs. Multiple SSIDs (AP interfaces) running on the same radio obviously do have to share a common ressource (plus some overhead) and you are limited by hardware to an upper limit of concurrent interface combinations (see "iw list"), so it's sane not to get too fine grained.