The only rule here is that you make your own rules; everybody is different and there is no 'should' or 'shouldn't'. If you don't want to offer unprotected services then don't - if the agency pimp doesn't like it then sack them and move on (preferably to independent work, but that's up to you). Never forget that agencies are a) illegal and b) need you FAR more than you need them.

Have you read the main SAAFE site? There are a lot of general safety tips on there, and if you have specific questions the search box here will turn up a lot of stuff too

A decent agency should not insist you do OWO. I'm surprised any agency would not allow it because that is likely to limit their clientele and subsequent income.
  I work for a few agencies that have let us choose which services we want offer( not including Bareback sex). Some charge extra for some services. Some are all inclusive. That depends on the agency.

Unfortunately anyone can set up an escort agency and they are not regulated. So the vary wildly in how they treat their workers and how much money they will make you. Some are run by people who genuinely care about your safety and well being and others by money grabbing  pimps who just want to exploit vulnerable and often inexperienced women.

They shouldn't dictate what services you offer.
They shouldn't take more than 30%(maybe more if incall is provided)
They should let you work when you want and not pressure you to work more than you want to.
They shouldn't allow "party bookings"(using drugs like cocaine)
They should allow you to choose not to see a client again if you do not want to( for any reason)

That's a few tips off the top of my head.