The root problem is quite common on that model and just removing the dGPU drivers for the Radeon chip one way to get it "to work" again.
But that leaves you with a machine that still uses the AMD chip for display, just without the proper drivers for accelerated display and no proper thermal management for the dGPU.
For a better fix in software you might want to try this solution here:
GPU problem - Boot Hangs on Grey Screen. That will give you accelerated display using the Intel graphics chip and a certain amount of thermal management back.
The full set of drivers is necessary to use the machine and get thermal management. The fix described in the link does work with High Sierra, but the drawbacks on that system are more numerous than with Sierra.
One problem with this solution is that on High Sierra the keys for display brightness will probably not work correctly. (Compared to Sierra Apple changed how that works/how that depends on GPU status or proper drivers…?)
To work around that, use macOS Sierra, that will also give you an overall much better experience in this situation. Alternatively, staying on High Sierra you might resort to using a software solution like Brightness Slider (free, AppStore-link) or a similar software. With Brightness-Slider you may even set up separate hotkey combinations for brightness control.
The sleep issue also gets worse with High Sierra. With the above "solution" linked to this should work well for a time, unless you connect too much peripherals (primarily to the ThunderBolt port) and it gets progressively worse, if you let the system go to sleep with these peripherals connected. With Sierra, Lid-Close-Sleep can be restored by re-setting NVRAM/SMC once the problem pops up. For both versions of macOS a more convenient solution is to avoid system sleep via lid-close. This is triggered via SMC and in the above configuration the data in SMC/NVRAM will eventually prevent proper wake.
To work around that, avoid lid-sleep and always issue it via keyboard shortcut or the menu item.
Bottom line: if it is in any way feasible at all for you, try to stay on macOS Sierra 10.12 for this problematic machine and use the general fix provided at the link.