Which bug fixes do you consider indispensable?

What's the best way to check whether a bugfix patch needs a header or not?

If there is only one patch and the readme or webpage does not state it, you have to try one of the two options and test the game at the point of where the relevant code is executed, e.g. test if the bug is still present.

Edit: if you have the code offsets affected in the readme as an example, you can apply the patch and generate an IPS report (with Lunar IPS) and see if it's the good offsets affected.