TOS/TAS/Kelvin/32c
I like the TOS/TAS and 32nd century designs for pushing the envelope for what a star Trek starship could look like, instead of just iterating on the same basic designs over and over, or repeating generic Sci-Fi starship designs. A starship that's just a giant disco blob, a bunch of loosely-connected pods, or a space doughnut/colon~~y~~, are all unique ideas we've not seen before or since. Even the Enterprise was unique compared to the rocket-ships of the time, taking a lot of design work to give it that iconic look, unlike any other starship seen before.
By comparison, a lot of series after TOS/TAS tended to mostly iterate on the same design. For its flaws (like using a millennium-old drive mechanism), the 32nd century ships appear to try and buck that with radical changes. Chain and Courier ships look nothing like alien vessels of the time, and the Federation starships are rather different, with ships like the Eisenberg class being tall instead of wide, compared to previous Federation ships we'd seen before.
Kelvin is just a fun modern take on the TOS, even if I'm not entirely convinced about the interior, and like Discovery, lays the groundwork for the TMP style of ships, with their square-ish nacelle designs.