On KDE there's System Monitor, which you can customize to show graphs for CPU usage and temp, among other things, and GPU usage and temp too.

For in-game monitoring there's Mangohud, also very customizable on what you can show in the overlay

I don't know if you've tried it yet, but setting the "Haptic Touch" option to "Fast" gets you a bit closer to what you could do with 3D touch.

It's under Accessibility -> Touch -> Haptic Touch

Personally I like it better vs the default setting.