At cam4, if you don't register (which is free) and log in, you can't comment in the chats or click on the names of people in the chats to see their profiles or cams. You also can't mark a broadcaster as a "favorite," so you won't be able to tell when the ones you like best are on cam. Registering is very easy, and you can put as much or as little information in your profile as you want. You can even be a "gender unknown," which I find kind of weird, but whatever ...
On the other hand, if you're registered and logged in, the broadcaster will see your user name in his chatroom. (If you aren't logged in, he just sees that he has an unnamed "guest.")
This matters because some straight broadcasters don't like having men in their rooms. If it's a very popular room, it's not important because you'll be one of 50 or more, but if it's just you and him, I guess some people could find that awkward.
It also matters because many broadcasters - gay, straight or bi, male, female or trans - don't like it when people lurk. They want you to at least say hello. Since guests can't chat, they can't be expected to say hello. If you're shy, that could be an advantage to not logging in, although if you stick to the popular rooms it's not important because the broadcaster won't notice one more viewer.
In other words, there are advantages and disadvantages to being logged in, but there's really no reason not to register. You can always log in and out and back in again as you want, sometimes watching as a "guest" and sometimes as a viewer with name and profile.
As for gold membership, it offers the advantages of being able to PM other viewers (free members can't PM; they can only respond to others' PMs) and - a big, big advantage - watch more than one cam. It's not free, although at $20/month, it's pretty cheap.
Best idea: Go as a guest and hang out for a while. Then, invent a user name and fill in as much of the profile as you want. See how much you use the site. If you use it a lot and can afford it, go gold.