Creatures do spawn underneath floating plots, and as far as I can recall meteors cannot spawn within the boundary areas, though I’m afraid I can’t give you any specifics about how this restriction works.
When I had my floating gardens pyramid on Kol Huroo, I left plot gaps between the floating pathway plots and I never saw meteors land between them and my grid did go far enough that if it was possible, they would have; either way, having a build like this did allow for reaching nearby-ish meteors fairly easily.
Based on what I vaguely remember, I think the only way you could get meteors to spawn in-between a plotted area like this would mean leaving enough plots open in-between plotted areas that anybody else could potentially place their own beacon in there.