Unless you were dialing up to CBBS between 1978-1980, i.e. the only BBS in the world at the time, then USENET predates your BBS era, which I would assume like most is really somewhere between 1984-1994, even if BBS existed prior to then and after then.
I remember reporting a PINE newsgroup thread bug at the height of my nntp usage and several of the local BBS systems had started dying off by then.
Especially the commercial BBSs could have quite a few systems and phone lines and, as you say the bigger BBSs often became the first ISP that consumers had access to if they didn't have access through their company or university.
You also had the big commercial services like Compuserve, AOL, Bix, Delphi, and so forth.
So in that sense BBSes would predate Usenet for most people.
I got Usenet access before I got full internet (even dialup) in fact but it was much later, in the mid 90s, using a really expensive UUCP account.