Vlad I'm not too sure how Chromium does it, but it seems to handle passthrough quite well. In terms of "crucial shortcuts", these would be shortcuts that allow you to navigate the browser (cmd + Q, cmd + L, cmd + n, cmd + shift + N, cmd + T, cmd + shift + t, cmd + M, and probably a few others that I am forgetting).
Essentially the goal is to pass the maximal amount of shortcuts through that don't cause you to lose any browser functionality