Is the setting your system to primary to be able to gameshare your PSN purchases still limited to two systems? I am wanting to get a third system for the bedroom but only want it if I will have instant access to my PSN purchases for quick pickup and play. I would test it out myself but I don't want to be stuck with a system that won't be able to do what I want it to do. Thanks
Primary PS4: Any account can access/play your purchased games
Any other PS4: You have to be online and logged in to your PSN account in order to access/play your games.
So you shouldn't have any problems accessing your games on a third PS4, but you can't play the same purchased game on all three systems at the same time (only two, your primary system and one of the other two PS4s).
To chime in here, the gameshare works slightly different than Xbox in case you are doing this and expecting exactly the same. Everything above is correct, but Xbox also lets others play your games in their profile on any console as long as your account is logged into that console at the same time and just sitting idle in the background. This doesn't work for PSN. This has been highly useful on Xbox for me in a house full of kids with consoles in different rooms, but there's a limited number of people who care about this.
The only other thing i'll add is that PSN is kind of a pain for transferring saved game data, so if it's your plan to play the same game in multiple rooms on random occasions, I don't recommend it. Xbox is much better for this since games are automatically synced to the cloud much better and more seamlessly on that console.