I have used Ballistol extensively, and tried it for numerous things.
It is an oil, and will not replace a grease. Where a thicker grease consistency is needed, use the grease. I still used a grease on the cylinder pin of percussion revolvers, for instance. Bore butter iirc.
It will clean. However, soap and water for blackpowder is cheaper, and still faster. There is one cleaning use that Ballistol does give. If shooting a lot, such as a Cas match, and you get home and just don't feel like cleaning, Ballistol will save you. Just spray some down the bore, and a light coat on the whole outside. You just want complete coverage. You can wait as long as you like, so long as it is at least 2-3 days minimum. Then, skip the soap and water, just push clean patches through, and wipe the outside. About the third patch will come out clean. It will clean more fouling out of a smokeless gun after hoppes will no longer get anything out.
I used to just wet them and clean a couple days later every so often. Once, came home with wife sick, sprayed them and took her to the hospital. They ended up removing her appendix. Anyway, forgot the guns on the table for over a month, two percussion revolvers, a winchester, and a shotgun. They were all fine. I was using goex blackpowder.
It will also neutralize corrosive priming from surplus ammo. In fact, it was developed in Germany during Wwii for cleaning corrosive priming from guns.
Never used it as a bullet lube, or patch lube. I would think it's not heavy enough for that.
It is a good protectant. Keeps finger prints from rusting. Will mix with water, water evaporates, Ballistol still left behind. Cleans better if mixed with hydrogen peroxide, but not really better than soap and water. A little dawn and as hot of water as I could stand were always my favorite.