Well browsers are apps, just like any other app on your system. So the same advice applies. If you don't trust chrome and firefox but you still want to run them, use a container/distrobox/VM. There are plenty of more private browsers though, like Brave or Mullvad Browser.
Web apps, on the other hand, run inside the browser sandbox, which is an entirely different environment. They don't have access to machineid unless the browser gave it to them, for example via a browser extension. There's still a lot of fingerprinting vectors though, so use Tor Browser or Mullvad Browser, ideally with JS disabled. This website is a great way to check your fingerprint: https://abrahamjuliot.github.io/creepjs/