My definition of conventional reels is :revolving spool, star drag, no levelwind, single speed.
All other versions are basically improvements on the original design.
You can cast with them, especially the smaller size ones, but once they get bigger than maybe 2.5"-3" diameter, it's more of a lob, than a cast.
Never thought of it that way, always figured revolving spool vs spinner. That definition could work as well.