If you add VG, you'll get more vapor. If you like a nice cloud (and I do), 20-30% VG will do the trick.
What will get you that ratio depends on how much of each flavor you mix. And, of course, don't forget that adding a doubler rather than an e-liquid will dilute the nicotine strength of what you are vaping.
You have cappuccino that is 11mg, 100% PG that you want to mix with a doubler that is 50% PG
If you mix it with an equal amount of that doubler your end result will be
5.5mg & 75% PG (25% VG)
If you mix it 2/3 e-liquid and 1/3 doubler your end result will be
7.4mg, 67% PG/33% VG
Also, caramel is another good flavor for cappuccino