n̥ is just the "not" prefix. The "ero" is the real root. The prefix applies to the root first, and then the other pieces have their meanings, usually. (Its a reconstructed language. There are both exceptions and things we don't know.)
"n̥-s-ero-" is sort of < "not" next-is-plural "mine" >.
So, plural-(invert mine). Or roughly close to "we".
"n̥-h-ero-" is sort of < "not" next-is-inclusive-plural "mine" >.
So, plural-(group (invert mine)). Or roughly close to "us".
But both are pretty close to the same meaning. High German maintained a lot of PIE, and is very close in a lot of ways. Though... Welsh is closer.
I feel like nasal sounds being associated with negation must be even older than PIE.
I've never heard of it being based on that root before. Do you have a source?
The two big ones for discussing Germanic languages and their inheritance would probably be:
"From Proto-Indo-European to Proto-Germanic", Ringe.
And the simpler "Lexikon der indogermanischen Partikeln und Pronominalstämme", Dunkel.
Both use "n̥-s-ero-", though in the more traditional /ˈun.se.rɑz/ form.