Maltodextrin is digestible sugar, so you have to count it in your carb count. I don't think there's anything especially bad about it, if it doesn't overload your carb count. Powdered sweeteners are mostly the bulking agent--effectively, a gram of stevia, splenda, aspartame etc. sweetener in powdered form is about a gram of net carbs.

Great Value also puts another line of stevia out that comes in packets and is bulked with erythritol, that really does count as zero carb, but I haven't seen it in loose form.

There are also tablet forms of various sweeteners that are basically zero carb, those might work for baking in recipes where the sweetener can be dissolved in some liquid before being mixed in.