Hi Tony, great to see you here on the ECF.
So VG is thicker than PG and so you'd expect a higher ratio VG
juice to be thicker and slightly more 'clingy' to the inside of the clearomizer walls when cleaning. Most of the juices I vape are 100% VG and they do need a good bit of shaking and agitation to remove all the traces of the juice inside the clearo. I would say this is perfectly normal.
That said, you say that both stores have the same ratio on their juice bottles. Usually flavorings are PG based, and so maybe (and this is a pretty big maybe) one juice has more flavorings and they didn't include the flavoring PG in their calculations.
I am not sure what the whitish / foamy reaction you are seeing. I have not had that happen with any juice I vape. I am not saying it's normal or abnormal, only that I have not seen that with my own equipment. It could be something simple like a flavoring they use that I've not vaped before.
If the juices are indeed similar in ratios, you should notice that their viscosity is similar inside the bottle, although it's hard to notice a difference of less than 10-15% in the ratio by eye.
As for the question about safety, I cannot possibly answer as I don't know the vendors we are talking about. I would suggest you have a chat with both vape shops and maybe take a sample of both juices and ask for advice with them. They should have no hesitation in answering most of your questions - if not, it might be time to find new juice vendors.