Here is a new study that contains some very interesting material.
Here is one small part concerning Enantiornithes:
Four flight styles for living birds were used:‘continuous flapping’ (CF) (e.g. grebes, ducks and auks); ‘flapping and soaring’ (FS) (e.g. storks, pelicans and large raptors); ‘flapping and gliding’ (FG) (e.g. swifts, falcons and gulls); ‘passerine-type flight’ (PT).
sampled enantiornithines fall across the range of all defined flight styles
I have proposed that enantiornithines are the ancestors of many modern bird taxa. When it comes to flight style we see the versatility within enantiornithes.
And we already saw that they inhabited all the different niches.