I've not gone the UM road as of yet, but I enjoyed the WB arch. Angron gets to visit home, but Guilliman is very rude and crashes the party. Spoiler Course it prolly wasn't a very good idea for that Planetary Governor to have mentioned the legend of Angron, the slave who ran, either.
This is one of those questions that comes down to the legion in question and furthermore the individual within that legion. Some legions teach that their primarch is a direct link to the gods and therefore their will and a primarch's word are the same. Somebody from a Night Lords warbands may have zero veneration for the gods at all and therefore their primarch's ideals will hold sway. Except some within the Night Lords believed that he went mad by the end as was a despicable being. There is potential to have every possible answer under the sun within a single legion based on who you ask.
Its an ambiguous and interesting area of the Daemon Primachs power in relation to the gods and to other princes. There is a lot of Khorne fluff and stories that list various Princes as his "most powerful" Princes like Doombreed are stated in places to be the greatest champion of Khorne. I guess the Primarchs hold a very unique area as they should really.
I am loyal to my warband because the most important brothers are those that stand with you, not those of the same blood as you. As for Lorgar or Chaos it's Lorgar until I die. Chaos is just the truth Lorgar preaches, it's the truth behind reality. I have no loyalty to gravity or any other such law, they are just truth and tools to be used.
Novel "Talon of Horus": The Primarchs made mistake after mistake during the Horus Heresy and finally lost the war at the Siege of Terra. During the exile in the Eye of Terror the Primarchs took more and more interest in Chaos and neglected their legions. The traitor Space Marines regarded their Primarchs as losers, loyalty to their legions dwindled, so the traitor legions broke apart into warbands. --- The CSM serve nobody, not the Emperor who betrayed them, not the Primarch who failed them, not the Legion which has turned hollow. They serve either themselves or Chaos. Daemon-Primarchs wield respect because they are powerful warlords, not because of their blood-bonds.
The sweeping generalization a single author says about the nine Traitor Legions should be taken with a fistful of salt.
Word Bearers would be a big exception in your list. Legion is still united after the heresy. And Aurelian is even more respected, than he was before the Heresy.
