There is a separate training track for fed uniformed police that I assume they go through, I am confident that they do not go through the FBI Academy or any of the 1811 investigator track training. NPS Ranger would know better than I.
The Secret Service has a similar model - the Uniformed Division guys are fed uniformed police officers, entirely separate from the Secret Service agent pool.
I'd hesitate to say that any of them are "just" federal beat cops - some agencies, like the US Capitol Police, are huge, and get into the shit on a regular basis. Others may have it a little slower, like the National Institute of Standards and Technology Police. But they all have their missions, and bad things can happen anywhere, anytime.