I want to know as well, everyone seems to have contradicting opinions. I know it has less treble than IE600 but people find that particular one bright. As long as it's no brighter than HD600 I'm happy
I dont own them so feel free not to trust me, but looking at frequency response graphs, I expect them to sound very different from each other in the first place.
They are bright in very different areas then the 600s. Basically, it is hard to predict if you will perceive them as bright.
The IE200 is bright in the mid treble (7-9k) which is an area where the 600s is rather dark. On the other hand, the IE200 is dark in the upper midrange/lower treble (3-5k) where the HD600 is slightly on the bright side.
While I expect the IE200 to sound warmer overall (more relaxed, less "shrill", but maybe also less clear), the mid treble area is where the IE200 is bright is a rather controversial area. Some people love a slight boost in the area as it gives a perception of "high detail", others perceive it as sharp and piercing. You most likely just have to check it out by yourself.
https://squig.link/?share=Crinacle_2023_Adjusted_Target,Sennheiser_IE_200_(D1)