Uff.. Cisco is, if you have nothing to do with networking, I think, not the right choice.
I currently also have the Netgear series as 5-port and 8-port. For me, IP TV (Sat to IP converter via Netgear to the server. From you to the media PC over two Netgear) works very well.
However, there are also switches that do not support igmpv3 or do, but it does not work well.
600€ just for a switch in the home area would be too much for me personally, despite the playfulness. You should keep an eye on power consumption.
Regarding double NAT, unfortunately I have it at the moment as well. The Nintendo Switch does not handle it at all, other consoles neither. A separate network helps here (which I have anyway) and no NAT from the device to the 1st router but routing. The first router is taught the IP route. This way you have some control over the devices. But it is different. So far, I have not been motivated to buy a pure modem, as there are always problems with that (depending on the provider), and with my provider, IP telephony does not work so well with the dial-in data you get from them. So I currently have a Fritzbox as router and telephony, behind it an OPnsense firewall.