As a follow up, I have tested the before mentioned "solution" for a while now with the following results:
Setting Frame Limiter to 60 indeed makes the game much more stable but FPS crashdowns with resulting lags do still happen occasionally. Like, every-few-minutes-occassionally.
If I set the Limiter to 30, it shows stable 31 FPS and the game runs very smoothly. When I did the Ley-Line Anomaly with the usual horde of people the FPS went down to 19 but there were still no lags. Only once so far, during Octovines in Tarir, it went down to 9 and I actually had a bit of lags.
During Loading Screens the FPS go down to 9, then up to 63 and then back to 31 when the loading screen ends.
So my assumption is that in one of the last patches something went wrong with the graphic-engine or the way the game communicates with the graphic card/driver since it just started being like that recently and only on my Laptop with the most recent graphic card of all of our 3 PCs.
Like already said, its an Nvidia Geforce GTX 1650 and updating driver didnt do anything.
Would be nice if this could be fixed in one of the next patches