Sith Troopers?

What confuses me is what the Sith Troopers and Sith Fighters are and where do they come from?

Sith Trooper Armor is very much a variant of First Order stormtrooper armor visually. So they clearly come from the First Order.

Therefore if this ISD fleet is the long forgotten Imperial Fleet everyone is hunting for, a new canon katana fleet as it were, these Sith variants cannot be onboard the ISDs upon discovery.

However the ISDs have red markings as do the Sith Fighters and the Sith Troopers, which implies these all belong together as a group. Furthermore the Sith Fighters have black wings like Imperial Ties, rather than the white of First Order Ties, potentially implying they belong to these Imperial Star Destroyers.

So I wonder if this could mean the First Order will find the “Sith Fleet” first and crews them with a special force loyal to the Sith? But Kylo isn’t a Sith?

What if Hux betrays Kylo and purposely or unwittingly hands authority of the First Order over to Palpatine? Or Kylo concedes power to Palpatine? Then Palpatine organizes a loyal force amongst the First Order and dubs them Sith Troopers and such?