I don’t like him. He’s angry at everything and his videos are a chore to watch. I also feel like he’s sometimes a bit out of touch (I don’t like ads or paying for digital content either, but if no one pays for it, it‘ll stop existing) and a bit pessimistic (yes, companies aren’t your friends, but not everything you perceive as negative is done out of malice, sometimes people are just not thinking stuff through).
However, I do appreciate him as a right to repair activist.
Glühwürmchen definitely refers to the flying variant. Might also refer to non flying species but I’ve never seen or heard anyone talk about any of those. The term is probably just used for any type of glowing insect, no matter if worm or bug.