i would put them between jalapeno and serrano for heat level.
i believe what makes them appear hotter is the bad ass placenta. so much like bishop crown or rocoto with the large placenta you only have to start munching and that heat just builds, of course you would be wise to remove the seeds - after harvesting a bulgarian carrot for seeds, you will never have to source them again....a pod houses plenty. perhaps rocoto is a good comparison for heat level.
as your plant matures, take notice of the flowers, in my recollection, i can't think of a pepper with a larger flower. kung pao has a nice large flower but is umbrella in shape but b/c is just massive like a starfish shape but i have never grown the likes of anaheim, ancho or new mex types, perhaps they rival in size.
on eating the b/c, the first thing you will notice is the crunch, they are crunchy. next will be the flavour, it is tasty. though some members have mentioned they didn't like the flavour, i found them quite tasty. then the heat hits, low key at first, then keeps on building.
here is a pic of my b/c, kind of nice how it turned out with the little helper. the plant gets potted up mon/tues as i move the tomatoes into the ground and free up greenhouse room.
hope you enjoy your bulgarian carrots.