Network switch selection for VLAN design

If your main goal is just to isolate your IoT devices from the rest of your network, you probably don't need to replace every switch right away.

I'd prioritize replacing the switches that actually need to carry multiple VLANs (trunk links). Any switch that's only serving devices from a single VLAN can stay unmanaged, as long as everything connected to it belongs to that same network segment. The important part is that the links between your router and the managed switches can carry the VLAN tags correctly.

The GS3xx Easy Smart switches should be fine for a straightforward home setup with a few VLANs. They're not as feature-rich as fully managed models, but for creating separate IoT, LAN, and maybe a guest/streaming VLAN, they generally do the job without being overly complicated to configure.

One thing I'd also think about is whether your Netgear RS router supports the VLAN setup you want (inter-VLAN routing, DHCP per VLAN, firewall rules, etc.). In my experience, the router's VLAN capabilities tend to be the limiting factor more often than the switches themselves.

Do you know which exact RS model you have? That would make it easier to say whether your current plan will work as expected.