I think, there are only three Locomotives with simulated ETCS:
K-Trains 193
K-Trains 186
ChrisTrains 186 (simplified)
The Traverso from Simtrain has also ETCS on board. But this train is based in Switzerland
If Fahrphysik and realistic breaks are important, don’t go for the Traverso, it’s only suitable for AI traffic in my opinion.
I too would very much recommend K Trains’ 193 for physics, sound and realism in general. Many different security systems are implemented, including ETCS L1 LS (PZB for DE, ZUB for CH) and L2. However, it has a very elaborate set up procedure. But if you go through it in detail once, you can use the quick start functionality thereafter, so you don’t need five to ten minutes to set it up each time. As I don’t use quick start, I however can’t tell you how well it works.
Then I hope you don’t get mad by the constant click-clack of the levers and the bad break physics, it made me furious 
Just to make it clear: you won’t need ETCS on the currently available Swiss routes for realism, but ZUB. In your case I would thus rather go for a TrainworX loco like HVZ-D or Re 421 (comes with additional PZB for Germany and EC coaches) or an EMU like DPZ. Or the FLIRT RABe 523 EMU Add-on by Rivet might be a good deal too: great model, a little less realistic physics, but IMHO still better than Traverso.
These all have ZUB implemented in a more (TrainworX) or less (Rivet) realistic way, that’s what you actually need for Gotthard or Zürich-Olten.
Here’s the Re 421 bundle, might be worth a look: https://www.trainworx.nl/product/re-421-pack-2021/
