Agree with everything Jazz01 has said there.
Fast.com shows a fairly consistent 1Gb/s download, 100Mb/s upload. Speedtest.net shows more like 950Mb/s down, 100Mb/s up. But that's because my PC has a wired connection, Wifi speed tests show more like 100Mb/s (from an iPhone11 with decent Ubiquiti access points, also wired).
I had Virgin Media 350Mb/s over coax previously and to be honest notice no difference at any time other than downloading large files. We'd be fairly heavy Internet users with lots of smart home devices connected, multiple PCs/phones online all day and two home workers. Next time around I'll take whichever is cheaper between Virgin Media cable and Eir/SIRO FTTH as gigabit is not necessary for our usage currently.