For Galaxy Watch4 and later, you are not required to have a developer license (or a watch face design partnership with Samsung) in order to distribute watch face designs. Watch apps developed for Galaxy Watch4 and later are distributed through Google Play Store.
Samsung doesn’t make any hardware recommendations other than what is necessary to use our tools. However, perhaps the developer community here may have some insights on what they use and why.
Please be sure to search through the forum to see if any of your questions have already been answered!