(1) I have one solitary rafter tie in the middle of the shed right now. My intention is to build out a loft at 7.5' across the body of most of shed, and I'm hoping that the "joists" of the loft will provide some of the structure that would normally be provided by rafter ties or collar ties. So far that one board is a champ, though. I didn't feel the budge with my weight at any point.

(2) The 5/8 OSB on the roof provides a lot of strength through tension as well, it's screwed down into both the rafters and the blocking. I worked a lot while sitting and standing on the roof, and didn't feel any movement when putting weight on the eaves. I've never done anything like this before, so I'm not sure if there are better ways, but I've also seen people put the last regular rafter offset from the wall and then have the blocking out to the fly rafter cross over the wall, like this:

https://images.app.goo.gl/oJ2vw4sG1f5tKc3w5

In my head that seems like it would be stronger, especially for distributed loads like snow, but I believe that would not be an issue for an overhang this small.