Helion's scheme would require a specific isotope of helium, of which there's not much of in current stockpiles. Assuming that you had some He-3, remember that since this is a reaction between nucleons, the typical energy scales are a million times higher than typical chemical energy scales. Therefore the amount of fuel (in kg) is a million times smaller. And so, there's a significantly larger margin for extracting and purifying the helium fuel from whatever source.

> Will the total output in electricity be greater than the inputs for this?

Yup, that's the goal!

> Extra: what happens if there’s too much expansion or things are too hot?

Fusion reactions are difficult enough that if it were physically possible to make them run 'hotter' or release energy faster, frankly we would already be doing so.

> Could this explode or implode? If so would it be a huge deal?

The radiation risks from fusion are orders of magnitude smaller than from nuclear fission power. We still need to think about them and make sure that plants are safe, but it should be significantly easier to manage.