Teamviewer can down-scale my remote 4K monitors to my local 1080p and it shows multiple screens at once. But this is an unrealistic connection speed for the average user and it wastes bandwidth. To prove it, I lowered the remote mac to 1080p or less, and unchecked "Monitors as individual windows" and got ~30fps where before I only got ~3fps. Now i'm flying!
All users won't try this though, so they'll never know how fast it is. It would help if the fps was detected by Teamviewer and it had an option to automatically try diffferent system settings to get a minimum of say, 15fps. An automatic configuration so to speak : )