Hello,
Yes RWE 2 need to cook the data at every launch. To be more precise, when you launch it for the first time, RWE 2 will scan all your Train Simulator data and store it in some "database" files, this process can be quite long depending on your installed content. After this initial "full data cooking" is done RWE 2 will need to load this data from the database files for each launch of RWE 2, this is called the "quick cooking" it is faster but can take some minutes if your content is huge.
There is no way to avoid this process unfortunately but i'm working on some solution to make this process the shortest possible
If you just start the game from steam without launching RWE 2, you will keep the enhanced visual effects but all gameplay features of RWE 2 (sounds, HUD...) will not work.