I have been told that any of the artificial susbtitutes that end in “tol” may cause tummy issues if used too often.
Stevia has no calories and can be used for baking (as can Splenda, but personally I don’t love the taste of Splenda and you need to use a lot of it to get the same level of sweetness as with the same amount of sugar).
BP Totty, I seem to recall seeing a hechsher on a package that I saw once, but did not end up buying. I could not tell you for certain. My personal info comes from what I have read or heard about it, not from use. I definitely WOULD use it if I found it in my kosher supermarket or elsewhere, with a reliable hechsher. It is made from a plant.