It's nice to have the fastest Wi-Fi possible even if your upstream internet is slower. Sometimes you want to transfer files locally between devices, or run backups etc. Faster Wi-Fi here can make a huge difference to those tasks.
I have found that higher tier WiFi aids local game streaming significantly, but most of that benefit seems to be the 6Ghz band that you get with WiFi 6E.
When talking about network bandwidth, it is custom to measure in bit-per-second therefore the "bps" notation. If you convert to bytes, it is highly recommended to use "b/s" notation instead, i.e 150MB/s, to avoid confusion.
But IIRC the de facto unit for network transmission speeds are bits - not bytes - pr second, and when it’s more the rule than the exception than people write ‘B’ in stead of ‘b’ then the confusion gets even higher..
I would expect this crowd here to not make these mistakes as ofte. :-)