So, I like this little amp very much, and am going to order one soon. I have just one question.

Given the amp's small headroom, can using a booster with it (Marshall Bluesbreaker specifically) lead to overheating of the tubes or any other problem like that?

Don't mind the noobity behind the question, because this would be my first tube amp.

So i'm asking you!
You don't need any pedal to play blues with it. The natural gain when cranked is insane. What kind of blues are we talking about? I play hendrix stuff and on 4watt near cranked it sounds really good.
I play Rory Gallagher mostly. So we're talkin blues all-around.
That's exactly what i thought, i don't want to use the booster for the volume boost, 4 watt all-tube is loud enough, but for the tonal expanding.
You'll be fine without. Nice little unit for recording, too.
It's an opinion. It's subjective. And I'm right, anyway.