I bought FSradiopanel, which in fact provides not only a radio panel, but also a basic PFD (primary digital instruments), moving map, gear and flaps panel, autopilot and more. I use it with 3 Android phones and 1 tablet and it's a great addition to the 4K primary and FullHD secondary screens!
But I was wondering if there's a way to see a complete Garmin G1000 PFD on the tablet and Spacedesk seems to be worth trying.
As for touch screen, it's great for buttons, good for handles, but so far quite a disasters for knobs (turning them). Sliding is supported with FSradiopanel, but it's a fight. So much that I'm thinking of purchasing some HW, i.e. HW autopilot panel.
Downside of Spacedesk, I expect, would be that the extra screen is still processed by the PC, specifically the image by the GPU. Having a 4K+FullHD on i7 notebook is already a bit of stretch, one extra monitor might be too much. With native Android apps like FSradiopanel, the external device gets only data (altitude, speed, flaps settings, etc.) and it creates itself an image of the panel(s). The performance impact is unrecognizable, I'd say.