I can´t imagine that you have such a potato machine that the game can´t work well.
Before I upgraded my old Desktop (Core Quad 9550, 4 GB RAM, Ati RX570) with a new board, Ryzen CPU and 32 GB RAM the game was also running without troubles (with GraphicsMod enabled), only the loading times where boring until I transfered the game from old HDD to a SSD.
So I guess your HS2 is crying out for a complete new install.
Did you make your upgrade from R11 to R12 via upgrade file from here
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If so you should also make a new download. My experience from this thread is that the upgrade way often is leading into troubles.
How to make a perfect install was posted here 1000 times.