Somewhere in between, full-time lecturers (called "instructional professors" these days?) were and still are exceedingly rare (albeit probably safe to assert all ECE alumni of roughly the past 2 decades were Schwartz'd and/or Gugel'd in some capacity).
The fancy/official term for this is usually Lecturer. It’s a permanent position that’s usually not equal to professor in power and prestige, but it’s permanent, the pay can be good and you don’t have any expectation of research.
Graduate students and adjunct professors have largely taken over this responsibility because they are much cheaper.
Not sure about that[1], but acknowledged.
Graduate TAs were par for any course with a lab component or recitation, even courses that were taught by a lecturer; never felt like I was somehow being shorted opportunity in those though. It's the infamous adjunct part that my experience draws a blank on.
[1] https://fora.aa.ufl.edu/docs/10/2019-2020/Faculty%20Senate%2...