Not sure if this is the correct place to post...

I've had the PS4 version a few days, and now my wife decided she's interested in playing too. We have a PC, and plan on buying that version and getting her a subscription.

What we're trying to do:
Both of us want to play, with one being on PS4 and the other on PC.
HOWEVER, we each want to go between the two platforms (PS4/PC) (to trade between couch and desk )
Can this be done by logging in via our own PS4 user accounts, starting up the game, and logging in with whichever subscription account info?
Conversely, can the same be done with PC?--using the one PC copy for multiple player subscriptions?

Reiteration: We want to play at the same time, one on PC, the other on PS4, but want to know if we'll be stuck on the system/reg code we originally registered our monthly sub on or if we are free to choose either platform as long as we have our own subs (which is what we're aiming for). Hope I described well enough-! =)