Where nonbinary folks sit on the sexuality spectrum is a whole other issue that's only gonna be more confusing if you don't know much about trans issues already, so ngl bringing nbs up kinda hardcore derails the whole convo. I think its an intercommunity issue so it's not really something that fits here. Basically I'm saying I think the person replying to you's in the wrong but also calm yourself plz
Atm the best way to describe bi vs pan is pretty much just what someone's more comfortable identifying as. Functionally they're the same thing, though, since nonbinary isnt a social class unto itself. Example: Janelle Monae is fine with folks using both interchangeably to describe herself, but Lady Gaga strictly defines herself as bisexual.
I guess it also confuses stuff since not all NB folks id as trans? There's a lot of afab lesbians that call themselves cis since in the Real WorldTM they don't face transphobia in any tangible way and are attracted to girls as women, but also ID as nonbinary because the particular way us lesbians experience womanhood in a heteronormative society is, unique, to say the least. But that's a whole other discussion (that I don't like having with non lesbians)!
With pan vs bi I think the best method is to not think about it too much