(I have a ryzen3 3200G with Vega 8 gpu and 2 x 8GB 3000Mhz of ram)
As you can see from the VIDEO attached, the game is really struggling.
As far as I can see, the problem is not from the CPU as it is reaching it's max clock speed and I don't think it's memory related because when checking the F3 menu the game still has about 750MB of Free allocated RAM.
I think the problem is that the graphics card doesn't reach it's max clock speed of 1250MHz and hovers around 900MHz and doesn't reach anywhere close to 100% or at least 90%.Also the gpu is only using about 450MB of the 3GB that I gave it in the BIOS.
And the problem only happens with The Vault Hunters modpack.