can i still look around if i’ve accepted a bid?

Yeh you can hold it

Some fraternities will let you hold, and some won’t. If the fraternity where you accepted a bid finds out you’re rushing around other houses, they might drop you, but they probably won’t find out. Just don’t mention that you have a bid there, let alone the you accepting it.

If you want to be a weasel

Bids are not official until the fall semester starts, when official bids are extended and accepted.
Yes, a fraternity can extend a bid and say accept or reject, kind of like football recruiting. A fraternity may want to cap the amount of pledges they take and don't want to hold a spot for someone while they shop around.
However, until national signing day it is just a verbal commit. Same holds true for Fraternity rush, it is just a verbal acceptance until you sign your name on the dotted line during the official bid acceptance day.

If you reject their offer you obviously won't be on the official bid list in the fall and if they get word you are shopping around they may drop you as well.

Here is my advice don't accept a bid offer from any fraternity that is demanding you accept on the spot. You will regret it big time, choosing which fraternity is right for you is a major decision and you should shop around and find out what all fraternities are about. If a fraternity did that to me, my answer would not be NO but hell NO and proceed to turn around and tell them to kiss it as I walked away. They obliviously have some major internal issues they are trying to hide by coming off like you should be lucky to get a bid from us.