Hi there and welcome to my forum

Retrofit and VM are quite different actually. From what I know, Retrofit induces changes made in Kingdoms to M2TW to add different siege engines, oil and Lusted's unit balance. It does not fix a host of trait/anc issues nor address things on the AI side and general game balance side as far as I am aware or changes AI profiles to have them build more intelligently which VM does, in addition to having its own unit balance.

If you change your timescale in VM, it will not adapt automatically (for that extra files and scripts are required which may require kingdoms). However, I do have a tutorial to walk people through on what to change if changing time scale to make everything fall in line.
If you have troubles doing so, I am more than happy to make those changes and upload them separately for you for the purpose of this mod.