Some juices do kill cartos (in my experience, dark or excessively sweet juices will do it), but that doesn't mean they aren't good, worthwhile juices. They're just better for dripping
As for thickness and PG/VG ratio, it's a personal preference. I actually prefer thinner, PG dominated juices. But I've never noticed much of a difference in carto performance. Then again, the brand of carto might have something to do with it. But in general, to be fair, I don't use cartos much these days. I've found I really prefer dripping, or clearos when I'm on the go.