Which AirPods are compatible without iPhone? What about the new AirPods Pro? Which would be most suitable for the sport (gym)?
All are compatible. However, if you use them with android devices, you do not have all the features
Yes they are. But AirPods offer at Apple even more features that may not be offered or work on Samsung / Huawei.
Whether it is suitable for sports, I do not think so. There are much better, also Preisleistungsstechnisch ago. In addition, there's a lot going on in the sport, there's a demand for good-looking headphones, which the AirPods do not necessarily offer.
& the airpods pro?
I think the same, they do not give much. Only maybe that the battery is better. But if you want to find out the difference to the normal Airpods and the Airpods Pro, just enter it into Google