#1. Awesome dogs. Rescue dogs are the best.
#2. Heinz for sure. You’ll probably never know for sure unless you do do DNA testing, but..
#3 Why would you ? Do you really need to know out of curiosity ? X breeds are usually much more hardy dogs because of their mix, unlike pedigrees, so you’ll only be doing this for your benefit, not theirs.
All my own opinion, and of, course, there is nothing to stop you getting tests should you wish.
But, for the record, I’d say there is a bit of Lurcher in there, especially if she is fast, and has a strong chase instinct. Which only adds another flavour to the soup.
Whisky looks like my Jasper when he was a rescue pup. Soon put on weight though, and started to look more like a Staff rather than a skinny Lab after a few years of easy living in a house rather than a kennel. I’m not ever sure if he is 100% canine at times.