Super-slow-mo is the way to go, but as a Note-8 user, I feel your pain.
Being limited to such a short time frame is pretty lame..
The higher the FPS the better - as with more frames, the playback will be much more fluid / smooth..
More frames = more shots of the pellet moving, so obviously much better..
With 60 frames per second, you'll get less still shots per second, so you'll lose out on more 'movement'...
Also - with zooming... Since we're limited to 'digital zoom' vs optical zoom,
all that the camera is doing is using 'cropping', so in reality, it's just taking the same image, and
using just a portion of it - so when 'zoomed', you'll be seeing loss in image quality..
If you can do something like 720p / 120fps, that might work - since it's sort or right in the middle..
With the native camera / video app, I'm not sure what your S9 has to offer..
I know that with a recent update, Samsung or "ScamSung" as I like to call them now
actually Removed our ability to manually zoom in video recording mode.. It's ridiculous!
I found that an old app I have called "Open Camera" gives back that feature, and adds a few others..
Orion The Iguana Hunter also recommended another cam app to me that works really well..
You might also want to check that one out: It's called HedgeCam or HedgeCam 2.
Sam -