Rationing? In today's day and age? I have unlimited mobile data with Visible for $25/mo. It even has unlimited (slow, 5 Mbps) tethering.
If you use a cheap VPN (I use Mullvad), your video bitrate doesn't get throttled. But the tethered device also needs to be signed in on the VPN because WiFi tethering on the phone doesn't use the phone's VPN, at least on Android.
If you use Android, and you're clever, you can USB tether to a properly-configured Raspberry Pi using EasyTether, and have that give WiFi to all your devices at full speed. I have a 4k Apple TV, and I get 4k video on my $25/mo plan.
For a single device like one PC, all you need is EasyTether on that PC, and then you can USB tether your phone to get unthrottled tethering. EasyTether costs a one-time $10 payment for the phone app. The PC app is free. You need both.
Looks like they have a new $35 plan that doubles the WiFi tethering speed (to a whopping 10 Mbps) and allows 1080p video without needing a VPN. That sorta seems like a sweet spot for price vs. hassle.