You're welcome!

this was very helpful, thank you.

I would say 2-B, the shotgun one. It's rather short and does not require spread management, just aligning and timing.

What's the best one to get the "Don't miss a shot and kill everything" achievement? I thought 1-A, but that last fast target...

Ah, that one's annoying, the "More than 20 seconds remaining" condition.

The first wave can be done quickly, but the dog part needs to be done carefully.
The second wave is the difficult part that is probably messing up your bonus time.

You have to take out targets within the first cycle, when they're in the middle. It's possible to do so for the pirates, but for dogs it's more tricky, as due to the horrible TMP spread, it's easy to hit the sailors.

I focus on the skulls, letting the first wave of dogs pass, then blast the last wave along the first one. It relies on a bit of luck.

If you don't care about perfectionism, you can still get the bonus even if you hit the sailors.

I can't get the bonues time to trigger on 2-A, any tips?

Aha, no worries then. I figured you might be concerned about the checkmark.
To correct myself: challenge 4-1 (punisher/shotgun) can have 4 stars.
You never get a checkmark on these.

Score is 10,216 with 3 stars. Maybe there is just no checkmark then, though that makes no sense to me.

As a clarification, it does not show a checkmark on the token.

I don't think it's possible NOT to trigger it if you haven't got any penalties and/or your timer is low.
Is your score at least 8000 and there's not a single star shown?
it's even possible to check your best scores at https://game.capcom.com/residentevil/en/