Disagree. If you look the crew in the tholian web theyre sporting a similar insignia but not the same as the Delta.
Nope, it's the exact same one.
In the ENT episode "In a Mirror, Darkly", a subtly different insignia was introduced, for a subtly different starship Defiant
. But the subtle differences put together suggest that this was a subtly different universe altogether...
Its been established every ship carried its own insignia.
The exact opposite has in fact been established, with several ship crews having the arrowhead in TOS and further in TAS. There is no particular reason to believe that every ship would have its own symbology - merely that Starfleet uses a number of symbols, probably to denote specific fleets, each of which contains a number of ships.
Ship-specific symbols were supposedly in use back in the ENT era, when there were few ships around. Even there, though, the only ship symbols we really saw were those of NX-01 and NX-02.