TL;DR - to fix GTA IV stutters if your GPU supports Vulkan try DXVK method, if it doesn't support Vulkan then go to 4-step DxWrapper method
(should help in all other cases). Do not combine methods below, use only one of them! If you are still not satisfied with gameplay then you may have to read the rest of the article and/or downgrade to version 1.0.4.0