Magnesium Sulfate is Magnesium Sulfate.
"Ultra Epsom® Salt is the highest quality, pharmaceutical grade Epsom salt available. Ultra Epsom Salt is ideal for use in a variety of applications, including home, spa, and
garden."
I took two years of Chemistry but I can't remember everything. Sulfur alone is insoluble in water. Sulfate is soluble in water. That's all you really need to know about the two. Yes, your plants do need some Sulfur. How much exactly, I don't know but it's not much.
Just try running 5-7ml's per gallon of Cal/Mag and look at your red stems fade after a few days. That's if you have red stems.