There really isn’t one publication or place that lists salaries. Talking to residents at your school about what they expect in their specialty is probably a good resource. Salaries will vary widely based upon specialty, location, days worked/production, etc.
For my specialty (pathology), salaries are lower than in most other specialties. Starting salaries for both diagnostic labs and academia seem to be in the 120ish range from what I’ve seen lately. It’s easier to make more in diagnostics though, I’m 4.5 years out now and because I do extra cases above my quota every day I made just under 200k this year (for a 5 day work week but only 30ish hours a week because I am faster than average at cases). And because I can work remotely and live anywhere, 200k goes a very long way in my little rural town compared to how far it would go in a large city.
In regards to GPA, that’s going to vary. In a lot of specialties, especially the super popular ones with lots of apps, GPA is the first screening data they use to decide which apps to review and which to just toss out. Others might not put as much weight on GPA and look a little more holistically just like for vet school apps. It’s best to talk to the programs and see what they’re looking for in an applicant. But in general, yes, it’ll still matter (at least a little bit) because at the end of residency there’s a big exam you have to pass and your pass rate will reflect back on the program in future years.