Just asking question out of the blues, why we need privacy based browsers when we use mixing services or it is just an optional way to add more privacy to our transactions?
In general, IMO it is a good thing to add a layer of privacy regardless if you're trying to mix or not. If your ISP provider tracks you and logs the websites you visited, it can be a nightmare if those data got leaked and abused by other parties, or even your ISP in general. Such as blocking your access to some websites, an increase in scam e-mails, profiling, etc. On the other side, you can also argue that hiding your real IP address, in general, allows you to keep being trustless in the sense that you don't need to rely on the hope that Yomix or other mixers don't abuse your IP data or something similar. It is a win-win solution.
If using TOR really makes any difference then definitely we should have it either published on the YoMix site as well as have the corner of Signature code updated displaying TOR or relevant browser name for additional security or whatever purpose it may solve.
Nice suggestion. That being said, most users who use service like a mixer is usually well aware of how important privacy for their activity is. So using ToR is usually a requirement for them.