This is the plasma armed variant of the standard dreadnought.
Here is the photon armed battle cruiser.
And this is the phaser armed battle cruiser.
The Command Cruiser is based on the standard Heavy Cruiser, but has a little extra mass to accomodate a flag bridge.
This is the scout variant of the destroyer with some weaponry replaced by superior sensors and an area jammer.
The fast variant of the destroyer has slightly less weaponry, but extra manoeuvrability.