My friends and I recently challenged each other to list our top five starship classes and were surprised by how different our opinions were despite being generally in agreement with what we like about the various series.
Personally it was hard for me to make a definitive "top five" but here are some I rank highly in no particular order:
TOS-era constitution
Refit constitution
Discovery-era Bird of Prey (OG is good too obv but I love the HR Geiger-esque weirdness)
D'Kora class Ferengi ship
Not canon, but I love the original "Long-boi" Discovery design. It gives off some very cool art-deco retro-futurism vibes. Not very classically "trek" but I love it nonetheless!
I've always been a fan of the canon interpretation that anything other than the two nacelle pattern was because someone needed to compensate for something in the workload. Battleships (Federation-class variants, Galaxy-X) have 3 so one can get chopped off and they can keep on trucking, quads rotate through them to even wear/allow 'sprinting' for longer, singletons being 2 nacelles in a trenchcoat for cost/maintenance reasons (which explains why they're often proportionally oversized), etc.