EA writes that the November 4 Steam release will coincide with the start of Season 7. If you’re new to the game, simply boot up the Steam version and you should be good to go. However, if you’re coming from Origin, you won’t have much to worry about. EA says that all your progress and unlocks will carry over from Origin over to Steam.
Regarding the Switch version, EA has announced that it will be delayed into 2021. It will still receive cross-platform play, plus the most recent seasonal content, and feature parity. As to why they delayed the Switch version,
“…but in order to do justice to the game and make it into the great experience Switch players deserve, our team needs more time. This year has brought on unexpected new challenges, to put it mildly, and we don’t want to rush anything out.”