Well if you want quiet don't go with the first generation Sony A7 series, they are loud as are most dslrs (mirror slap). You might want to check out the Fuji X series, they have electronic shutter option (silent) and if you are still using film cameras their controls are similar, you can start using with no learning curve. They can take Nikon lenses with adapter and have focus peaking for manual focus, but they do have a 1.5x crop factor (you can get a pricey adapter that will allow you to shoot with no crop factor. They have both rangefinder and slr type bodies to fit your shooting style. One thing nice about the Fujis are that they consistently offer free firmware upgrades that improve functionality of the cameras and lenses:
https://luminous-landscape.com/rantatorial/fuji-keeps-giving-me-a-new-camera/
See Fred Miranda for used equipment:
Buy & Sell Photo-Gear - FM Forums