The pellets don't sink too fast, takes about 1:30 to 2:00 minutes to sink. The guy at the PetSmart told me they were fed micropellets and frozen baby brine shrimp, so I'd think that they'd be interested in eating the food.
I just introduced them to the tank, so I'm not sure. However, every time I do try to put in the pellets, my betta just goes om-nom-nom onto them, and inhales them. They really don't tend to make it past my betta, but I have tried putting the betta into a makeshift breeding box and letting the pellets descend. Even then, they don't eat it.
I'll definetely try to get flake food on my hand, although I'll still try my best to try and get them to eat off of the micropellets, that'd really be preferable tbh.