What @Cubic13 said.
Disclaimer
I have avoided ratings ever since because I am not absolutely sure where and how they are stored. So, there’s another grain of salt 
.
First of all: I assume all 3rd party VSTs are excluded because this would be a story on its own.
When it comes to write-protected files and their ratings there is a specific file in the folder Steinberg MediaBay Server.
MediaDefaults.xml
This file is supposed to contain the ratings of write-protected VSTs as far as I know. The Steinberg List of Settings Files and Their Purpose says that it contains MediaBay columns, lists, attribute settings and MediaBay settings.
When it comes to User Presets, well, I am not sure if their ratings are included in the above mentioned file or if they are baked into their presets. I assume that you need to transfer all User Presets anyways, because ratings alone won’t do the trick. Most of them reside here:
- C:\User\Username\AppData\Roaming\Steinberg (MIDI Loops or track presets, etc)
- C\User\Username\Documents (various folders with User Presets)
(Sorry, these are the Windows paths, you need to change them accordingly under your OS)
Maybe others can chime in as well. This is is still uncharted territory and there is no dedicated tutorial (at least not to my knowledge) how to transfer ratings with a step by step instruction including all Steinberg presets.
One last thing: Although you mentioned that you know how to transfer your preferences and key commands it might be a very good idea to save your current Profile as well. I contains not only both preferences and key commands but also other settings that are quite useful. Please make sure to save your profile proberly because there are some pitfalls involved. Here’s a tutorial in case you want to refresh your knowledge: How to Save Profiles, Key Commands, Preferences, Inputs/Outputs, CR Presets, Plugin Collections