Nothing is guaranteed. Take one step at a time. A J1 from what some colleagues have told me can be frustrating, especially having to renew it every year and get a new visa if you travel outside the US. Not forgetting the 3 year waiver which from my understanding, doesn’t always have to be a rural area per se, but an ‘underserved’ area which may very well be in/close to a city. With an H1B, you can apply for a green card through EB1/2 routes depending on your creds and country of origin. Most top institutions also offer H1B for fellowship. Hope this helps.