HUMAN BENCHMARK

Or can you just repeatedly click a few times in advance?

You can use the bomb at any time, but in that case, it will be consumed. The point is that it provides invulnerability for a couple of seconds and, as a rule, clears the screen. In short, you need to use them wisely.
In the case when you take a hit, there are 0.1 seconds to avoid losing a life; I can do this quite rarely, and if my reaction were better, it would be easier.

On the other hand, these games only require reaction time about 50% of the time; the other 50% involves memorizing patterns, understanding the level, and planning a route for completion. You use bombs more often in the most difficult moments or when you know in advance that you won't be able to dodge (or, no less often, when you panic).