To chime in on a few points in this thread...
The "Battle Cruiser" designation, as mentioned above, more of a "nickname" than an actual hull size. Though, being technical, the K'tinga is a variant of the D7, which the Klingons call "battlecruiser"...
For the Gorn, Lyrans and Kzinti/Mirak, their battlecruisers (BC) are more an upgrade of their basic CA hull made more combat-worthy, sorta like the Fed CA+/CAR+ in comparison. I think the Gorn did the name to make their CA+ sound more fearsome, the Kzinti to make their crews love the ship (cause they dreaded the CA), and the Lyrans because their CCs were reserved for nobility...
The BF Kroma speaks of is the Gorn G-BF or "fast battlecruiser". That's the Gorn's entry into the Fast Cruiser race, taking their BC (buffed up CA hull) and giving it the "standard" Fast Cruiser upgrade, it loses a couple of Plasmas (Pl-Fs?) for phasers, and gets stouter engines.
My studies of the SFB hull designs tell me the BCH series was designed to be the "best" combat ship that a normal Cruiser shipyard can build out of "standard" technologies. When you read the ship descriptions, the CW/NCA line was designed to be built in destroyer-sized slipways but give "CA levels" of combat capability. The DWs are built in frigate-sized slipways, to replace all the DDs not being built while the DD slipways are cranking out CWs. And, the BCH is the ultimate ship built in CA slipways.
Coincidentally, the BCHs were also designed to all weigh in around the same size, 180 BPV. This was done as a "pseudo tournament" ship...
Going by "SFB Lore", oddly enough, in a straight out "exploratory" role, the Early to Mid-era CAs are "better" explorers than the BCH because of lab ratio (lab ratio = # of labs vs overall # of boxes/systems), fuel effiency (aka move cost) and staffing (crew) needs.
Meanwhile, the ISC never built a "BCH", mainly because of the ISC's late entry into the general war. Per SFB, the ISC doesn't really get into the fighting until the (SFC-timed) 2280 ballpark, when all the BCHs, CBs, CWs, DWs, etc. were already built. Because the ISC knew (thru spying) what everyone else was building, they built their ships to be the best of the era. The CAZ weighs in around 179 (SFB) BPV (low end BCH range) and the CCZ weigs in at a 209 (SFB) BPV or so, equivalent to most of the "fully droned out" BCHs (when using all the BPV additions for drones etc. per SFB).