Visual fuzziness of Necromonger actions/ships

It seems that for the fuzziness, it was simply a decision in style made by the visual effects producers, in order to maintain the visual style of Pitch Black (The first movie of the Riddick series), being "an ambiance of mystery in which you never completely see what's going on" as quoted in this Alain Bielik article:

One of the most important sequences we worked on was the aerial battle between the Necromongers armada and the fleet defending the main planet, Helion. David wanted to use the visual approach that had been so successful on Pitch Black, an ambiance of mystery in which you never completely see whats going on. Indeed, during the battle, the ships are never fully lit, but briefly illuminated by all the flashes and flak from the battle instead. The image almost has a strobe light quality.

The Helion ships were CG models provided by Double Negative and heavily modified by Hammerhead. Both companies created numerous shots involving those ships, but Chiang cleverly split the workload in daytime and night-time sequences, Hammerhead being assigned the later.

This second quote is more important as to the similarity to the "ghosting" effect of Lord Marshall, as they appear to be the same technique, which was used to create this "ghosting" effect of Lord Marshall, referred to as "Astral Effect" in the consulted article:

One hundred and forty of these shots were created by Double Negative under the supervision of Tom Debenham and Jesper Kjolsrud. There was one sequence that was pretty complex from a conceptual point of view, Kjolsrud says. The bad guy, whose name is Lord Marshal (Colm Feore), has the power to send his astral body in a direction and to project himself very quickly in its trail. During his climactic fight with Riddick, it gives him the ability to strike at light speed while avoiding being hit.

It also mentions that Double Negative did the CGI for spaceships and characters, which explains the similarity between the spaceships and Lord Marshall:

Besides character-related effects, Double Negative handled several complex shots involving spaceships.

As for the Astral Effect, it is actually a power the Lord Marshall has, as stated in the AWN Article and the Riddick Wikia (referring to Lord Marshall):

He also has the ability to detach his soul from his body, granting him super speed, by means of his soul quickly moving to a different place and his body following it almost in an instant.

In summary, although Double Negative did the CGI for both the "fuzziness" and "astral" effect, the first one was simply a visual stylistic decision which appears to be heavily influenced by the setting and terrain rather than the spaceship alone, while the second one comes from Lord Marshall's power to create an astral projection of himself.