I think I’m looking for contact seals on the external with open seals on the internal side
Those do exist, but it's much easier to get 2RS and they''ll be fine. If you're bothered, you can use a pick to remove the unwanted seal. All the major Euro and Japanese brands are good (SKF, FAG, NSK, NTN)
No, they're weaker than regular bearings. Applications which actually need stainless have corresponding larger bearings to compensate, bicycle hub bearings are already on the small side for the service load.
Those do exist, but it's much easier to get 2RS and they''ll be fine. If you're bothered, you can use a pick to remove the unwanted seal. All the major Euro and Japanese brands are good (SKF, FAG, NSK, NTN)