You have mentioned several flavors. Which goes back to balancing to meet a market expectation.
Chocolate as harvested has fruity notes and is compatible with either white or red grape juice. As cocoa beans are roasted fruity notes go away and bitter/ tannin like notes dominate. This is closer to a vinifera red tannic grape (not grocery store grape juice) and one could reduce the amount of cocoa or chocolate extract yet still have nice chocolate flavors by using a red vinifera. ,,, Some recipes will add grape juice for yeast nutrition not flavor, in this case it doesn’t matter which juice. ,,, US market usually consumes milk chocolate which has vanilla flavor, therefore adding a few drops of vanilla produces the expected flavor notes (1 or 2ml per 20 liters).
While on chocolate, ,,, cocoa powder is nasty, it traps gas therefore has to be used in a primary with extra volume. If you are adding/ doctoring a fermented wine use an extract.
Wine making is like cooking. Do you balance flavors when you cook? Then have at it. If you follow recipes when cooking it is worth while looking at several recipes to guesstimate how flavors will combine. ,,, welcome to WMT.