>...Can those be used with a regular shutter or am I better off trying to trade those for regular bulbs?

Well, those are bulbs with a different timing for the peak light output than class M bulbs. At really slow shutter speeds, it might work. I have seen diagrams, as in the old Kodak manuals, that showed the overlap of types and shutter capabilities. FP, or Fast Peak, or Focal Plane, were designed to flash in a hurry while both shutter curtains were open. Class M had a modest delay to give the shutter time to open fully, during the peak of the output. Put another way, the bulb timing allowed for the ballistics of mechanical delays built into the BtL shutters.

It might work if you have an F sync on your BtL shutter, too. However, most of the time nowadays, an F is the setting on the lens that disables the built-in shutter and allows it to be used on an FP body. When I was a kid, I remember experimenting with the FP bulbs and the X sync on my camera. It worked, to a degree. Most of the time, one gets insufficient light because the timing is wrong.

Although I grew up with this stuff and had to learn it years ago, it is now (fortunately) a matter of historical interest.