That states that the it is "Glycerin (USP Vegetable)" which is what is sold in drug stores, on Amazon and from vaping suppliers at lower prices. As long as it is USP and Vegetable, it should be fine.
That said, VG is noticeably sweet, so PG might be better for diluting flavor, especially since the OP mentioned too sweet as one of the issues. The two easiest methods were mentioned above: Get unflavored liquid in the same strength as the overly flavored and mix to taste, or get the flavored with a higher nicotine level and then dilute with PG, VG, or a mixture.
I don't like sweet liquids, so I have always gone at least 60/40 PG/VG, and now that I make my own it is closer to 80% PG.
I don't want to get into the whole safe VG discussion. It has been debated to death, but I recommended Vitamin Shoppe because it's local for many of us. Also, on the bottle itself it states "Natural Sweetener"
Directions say to "Add 1 tsp of vegetable glycerin to water or beverage of choice for a slightly sweeter taste."
So I know for sure that this one in particular is safe for digestion. That's all I'm saying.
I read countless threads about VG from various sites before I went ahead and got some. There were arguments for both sides on the safety of bottles that didn't specify for internal use. I never really chose a side, but it wasn't worth my piece of mind over an extra $2-3. In the end I only used like 1-2ml of it. I just decided to buy the right vg/pg concentration for myself.
That reminds me, I've always wanted to vape it by itself and see how it tastes and blow big clouds. I just never got around to it. At the time all I had was clearos that supposedly would have bad wicking issues. Still only use RTAs though, so prob still have wicking issues.
My local shop makes their own juice, and they wouldn't sell me unflavored base. Said I would screw up the nicotine concentration and the flavor of the juice. I didn't argue with them, and I haven't been back since because I realize how overpriced they are considering they are selling rebranded Top Vapor (madvapes) juice.