I would say my series is high concept, but could also be a mix of both. The basic premise could be summarized in an elevator pitch.
A poor girl and a rich boy learn they'll both be murdered in 1 year, unless the murderer is killed first.
That one sentence explains quite a bit: class differences, mystery, drama, and maybe even romance. With also a future promise of action and thrills.
Add mommy issues and blood curses, you get characters that will have a story regardless of the plot.
I feel like the plot and the characters are constantly fighting over significance lol. Without the characters, the plot would still drive the story (and vice versa).
or maybe it's just bad writing lol
Edit: I wanted to add to the discussion of what makes a story "high concept". You could have a one-liner that's just "average joe fights dragons" and sure, it's a simple concept, but I don't think it counts as "high concept" because it lacks conflict (or as Blake Snyder would put it: irony).
Without conflict or irony, "average joe fights dragons" would have to rely on good character development to be interesting, therefore making it low concept.
"half-dragon prince must stop the dragon revolution" is a decent enough twist, and with some work put into it, could even be interesting.
aaaand that's my two cents.