@KeilahH I’m not a biologist so take this all with a good helping of salt
But obviously a creature moves while flying “forward” and while flying upright can more easily hover
This kind of stuff is apparent in insects, birds, etc. and in all those cases the wing mass is pretty low
Flying upright generally involves moving the wings in a figure-8-ish and sometimes having multiple pairs of wings so that the ratio of overall lift/drag impulse on one stroke can be around 1, whereas only simple wing beats/extending wings are required for flying forwards
I think that for reasonable suspension of disbelief you would want a mix of the two - forwards when forward motion is required, upright when hovering in place - but also make sure the creature’s not too heavy or else the required wings will be pretty large
Fun thing is though, it’s your story; you can have them do whatever you want! I like things that fly, I’d happily suspend disbelief if they can move forward at 100 m/s while flying upright. In fact I wrote some characters that can do that in my world, too, it’d be hypocritical to criticize.
It's very much an aesthetic choice. Personally, I like bumblebees - their flight is sort of at an angle with their body at about 20/30 degrees off the horizontal (for the big, solitary ones in the UK anyhow). This is how they land too, rear feet first, then the other legs set down. Strangely satisfying to watch.
Cont.: Maybe your creatures land in a similar way - like the Black Widow (Marvel's version, not the spider). See NY post.
@KeilahH What you do is pick the one you want, and then position the wings on the creature. That will ensure that the flight is the one you want. It's not like winged beings can change.
