does this impulse have any dodgy new copy protection schemes? Like securerom? Just looking at the other posts and starting to worry its gonna be messy if i have a computer crash.
No, it doesn't. It just isn't published on SDC or released as a standalone, which means you need Impulse installed and the game registered with a valid key to download.
There's no new DRM scheme

stupid question, where does the patch go after its downloaded?
Doesn't go anywhere, it patches the game automatically

You always archive the whole game of whatever version, not the patch file itself, as far as I understand (I haven't used the archive feature yet).