I’ve used one of the Winexpert/World Vintners 1 gal wine kits of pinot noir must in a 5 gal batch of imperial gose (10.3%)
before. The 1 gal kits should come with a 1/2 gal bag of must that’s to be diluted up to 1 gal and fermented.
When dumped the 1/2 gal bag in the 5 gal batch, it increased the gravity by about 25 or so points, if that helps. Had GREAT results.
Frankly speaking, I think what varietal you choose depends on your own taste/palate. If you prefer a certain style of white or red wine, maybe try to find that grape or something similar.