"For me, one of the issues with the later Trek, is that some of the production people begin bringing ideas in from fandom and that these bits of data became canon. It didn't matter if they contradicted what had come before."
I wholeheartedly agree (e.g. "Constitution Class", turboshaft system of TOS Enterprise, "Mark IX" etc. - a friend from Australia who is into RL vessels pointed out that there has never been one navy ship with a "Mark" designation. It's only used for equipment).
Again, according to The Making of Star Trek
, the original term for a ship like the Enterprise prior to "The Cage" was "cruiser class" (in accordance with Jefferies original 17th cruiser design). And the Enterprise - according to Gene Roddenberry himself - was to be a "heavy cruiser".
When the series took shape they did change this to "starship class" (in HD the bridge plaque is readable, so you can't just dismiss this, IMHO). It's pretty obvious in TOS that this is the designation for a capital ship as everyone in TOS is keen serving on a "starship" and according to the 'Drunken Scotsman Nomenclature' in "Relics" and Scotty (TNG) he has served on "a freighter, a cruiser and a starship".
Eventually, cruiser became a type. The viewscreen display in "The Enterprise Incident" (illustrated in The Making of Star Trek
, buy this book!) labels the Enterprise as a "space cruiser" (in contrast to the Klingon "Battlecruiser").
There seems to be a difference between "space" and "star".
Kirk refers to Republic (NCC-1371) as a "United Star Ship" in "Court-Martial" though Pike already refered to the Enterprise in "The Cage" as a "United Space Ship".
IMHO, that reflects the original state of the early UFP (just a few star systems) in contrast to the later state which covered vast regions of "space".
Hence "star cruiser" would refer to an older type of cruiser while "space cruiser" is a term for a modern type (like the "Starship" Enterprise).
By the 24th Century it would seem "star cruiser" is a term applied as a colloquialism for any old kind of ship (Kolrami about the Constellation Class USS Hathaway in "Peak Performance").
I should add that I'm unable to find fault with the inscription of "James R. Kirk" on the tombstone in the second pilot.
As far as I recall having it read somewhere, the "R" was an abbreviation for "Rice", a derrogatory nickname for Kirk during his days at the academy.
Not only did Mitchell want to highlight Kirk's short career as captain of the Enterprise (started at stardate 1277) but also have an extra bit of evil fun of burying Kirk with his nickname.