Personally I only use peppermint for my mentol tasts so I would not try it with any other metol testing products. Use your own judgment, however I recommend you try peppermint. Also I don't have so much mentol in my recipes. I would use only about 2 mil for 100ml. Its not a cold mentol, just that sweet peppermint taste.
Marshellow would tast good, but expensice since it does not tast that much, at least from my supplies, anyone knows a good brand for that would be appreciated.
Also VG is vary sweet on its own. If you use 100% VG its sweet. You could just omit the sweetner if you don't like it.