Another thing i want to add but have no time for. It's planned but not available yet. 
There is an issue with APUs and bios modded GPUs, they can't go along on win 10 build 1803. There is a driver issue caused by win 10 (error 43). You must keep your original bios to use the Vega cores from Ryzen G series.
If I may advise you, better fixing the warm-up issue before.