Yes, provided you buy both versions of the game and link them both to the same account, you can alternate as often as you want playing on one platform at times and the other platform other times with the same character(s).
There are a few settings (UI layout, hotbars, gear sets, and macros) that are stored locally, though, and wouldn't transfer over. Those you have to set up separately on each platform you play on, and keep them up to date on each when you want to make changes. (The main reason I haven't added the PC version to my subscription is that I don't want to deal with that hassle, as I update gear sets fairly often. For some people, it's worth it, though.)
