I can’t be sure since technology has so many different factors, but splitting a single Ethernet out into multiple with a network switch won’t really affect it much if at all. Cat5e cable/jack (common for most cables) gets 1 gigabit, so unless you have a gigabit connection and maxing out the connections already, you shouldn’t notice it.

As for WiFi, even though a lot of newer technology is great, it’s not going to beat Ethernet.

I was in a previous update wave, and it made me switch to Jellyfin too. I cast from my phone to my TV, and they did something that made subtitles basically impossible to load via Chromecast. Even trying to automatically burn in subtitles didn’t work for this mode.

Also, while a “minor” nitpick, Chromecast used to show random movie/TV show posters when you connected and also show the media details when you selected something, now it just shows a big PLEX logo all the time unless playing something.