Can these black tapioca pearls be used to make brown sugar boba or do I have to buy a different kind?

I used these for Boba and made a simple syrup with brown sugar and mixed the boba in the syrup and added some syrup to the milk tea. I stored the syrup in the fridge to use again over the next few days. Simple syrup 1 Cup water 1/4 cup brown sugar 1/4 white sugar - book water and stir in sugar til dissolved. 3/4 cup Boba is perfect for two drinks. Hope this helps

About how many servings is in a bag?

That depends upon how many pearls you put into your drink. But easily 4-8 servings per bag I would say.

What is the difference of the black regular vs. Premium pack? Images and description are similar.

I’ve Never purchased the premium. But I can’t imagine it being any different than the black bow but it’s just a different brand it looks like using different terminology. This brand seems to have the best deals going you can even buy a four pack of 8.8 ounce for like $12 if you search