Your character will be on the same server regardless of platform. It's possible to transfer a character from one server to another, but it costs money ($18) to do so. When that character transfer service first started, SE did offer an initial period when it was free, so I suppose it's possible they could do so again, but it seems unlikely. (That free transfer period was because some server issues during the initial launch made it especially difficult to create characters on some servers, so a lot of players ended up creating characters on a server other than the one they wanted to.)

Your best bet is to try to talk your friends from the PS4 forums into making up their minds and choosing an existing server so you know which one to create your character on. Or perhaps you could pick a server yourself and talk them into joining you there.