I have an AMD 5900HS iGPU and a 3070M in my laptop. I've had no issues on Mint (with the auto-installed Optimus in the Nvidia Prime applet) or with PopOS. If you want to use passthrough, SR-IOV GPU sharing is not an option for AMD iGPUs IIRC, and I know it doesn't work for NVIDIA dGPUs, so you'd need to pass the whole dGPU through to the Windows VM to get hardware acceleration.
For Figma, I would say the unofficial Electron wrapper or the online version is likely your best bet in terms of reliability. If it's just using the browser mechanisms for hwaccel (no funky accessing windows resources behind the scenes) if you run Optimus in the "on-demand" mode the webpage should be able to access the dgpu for hardware acceleration just fine. Optimus is a lot better than it was a few years ago.