You are talking about Dimension-Strings.
If you are new to VSL and the complete amount of available Patches perhaps currently a bit confusing, it might be reasonable to start with the VSL-Presets, which gives you a good selection of the most important patches. If you are fine with using them, you might pehaps later consider to optimizse you presets.
Keep in mind, that RE (regular) will be your bread & butter starting point. The force string or openstring patches reflect special musical situations, not so seldom demanded written in the score. Thats a bit like the meaning of sul G-Patches for the G-String available in many other VSL-String-Libraries, But as far I understand this it not the "regular" way a violinist will play. If you ask for a general answer of your question I would suggest always start with regular, change when you are not satisfied enough with the result and one of the other patches does the job better.
The VSL-Dimension-String-Presets provide only a basic selection of articulation types while the patches available inculde much more variants. If you are smart and your Hardware powerful enough (large RAM, good SSD's good CPU) , try to build your own presets with as much variants as possible available, because I personally believe everyone would like to answer your question not in any general sense but individually for each single musical situation. It might be a bit timeconsuming work to set up more powerful presets, but this will make your use of VSL-finally most timesaving, most efficient and most versatile.
(I saw you ordered the Synchron-Strings: If we are lucky VSL will have done a good part of this job with Patches made for the Synchronplayer: "Play short notes, long notes with various attacks, legatos, scalable vibrato intensities and note repetitions with a minimal need to switch articulations, and by moving just one or two preconfigured controllers." That will make many things more musical reasonable. For previous Libraries you have to programm your presets your self in a way that gives you at least a bit of that musical freedom. With good RAM, SSD's and CPU it is at least already a lot more possible than the VSL-Presets currently provide)
I hope my answer was able to inspire a bit your own ideas to find your individual way to the most efficient use of VSL for your needs.