My OBS Looks different than someone elses - help?

I'm trying to help another user on this computer set up OBS for streaming, but it looks completely different and the canvas isn't "set" the way mine is. The whole UI looks different, in fact. They'd screwed around with some settings before I came in to help (forever ago) so that could be part of it. Same computer, so same version and everything. Here's what mine looks like:


And here's what theirs looks like, which makes it impossible to properly set it up as you can't tell where the canvas actually ends:

How do I revert it (or just change it) back to how mine, and most everyone else's looks? I'm sure this is something simple, but I can't seem to find it anywhere. I'd really like to avoid a total uninstall that includes the removing user settings, because it'll completely mess up mine and I don't want to have to redo it.
... I figured it out. Like I thought, it was simple, and I just couldn't find it.
For anyone else having this problem:

The canvas issue, right click, then go to Preview Scaling>Scale to Window.
For the colours issue, go to Settings>General>Theme> Dark (Default)