Is the difference from lip corner Botox more visible when you have a neutral expression than when you smile?

It looks fine when I'm smiling, but when I'm still, the corners of my mouth seem to droop slightly, making my impression look a bit heavy.
It's not that I'm in a bad mood, but when I have a blank expression in photos, I feel like I look tired or upset for some reason.
So I'm looking into lip corner Botox, and I'm wondering when the difference is actually most visible.
Should I understand it as the downward pulling force decreasing slightly when I have a neutral expression, rather than the corners of my mouth turning higher when I smile?
I don't want the shape of my mouth to change too much, haha.
I wish my impression looked a little softer when I'm just standing still.
I am curious if you notice the difference first in photos when you have a neutral expression after getting lip corner Botox.
I am also curious if your original facial expression remains almost the same when you speak or laugh.
I tend to talk a lot, so I think I would be really self-conscious if the movements around my mouth looked awkward haha.
Is it possible to receive a small amount first, check the results, and then adjust it for the next time?
I feel more at ease receiving it while naturally adapting, rather than seeing a definite change all at once.
Also, I am wondering if you look into the difference in height between the left and right corners of the mouth during the consultation.
Looking at the photo, it feels like one side is just a tiny bit lower, so even if I can't make it exactly the same, I think I'll be satisfied if the difference is less noticeable.
Are there any of you who have received lip corner Botox and felt highly satisfied when looking at photos of yourself with a neutral expression, even though those around you didn't notice?
I would appreciate it if those who have received this treatment naturally, without any discomfort when smiling or speaking, could share their experiences.