Emmrich > Solas

• Look for the mesh you're going to replace with. (I replaced Emmrich with Solas because I want to see him as Solas, so I used Solas's mesh)
• Copy the bundle
• Replace the Head_Preset and Body_Preset
• Add an entry for every bundle you use in the Level > Root > RootLevel > RootLevel > description; add a new entry (+) to the "Bundle" and "Super Bundle"

It works for Replacing Companions with NPCs

Strand/Non-Strand Compatibility

How to make stranded hair compatible with non stranded hair (in the description file for library mods):

You will need the strand bind asset bundle

• (eg: characters/actors/morrigan/hair/models/f_har_morrigan_01_strandbindasset_bundlegenbp_autobundlegen)

An NPC convo bundle from the same NPC you are replacing the hair with

• (so if you want Morrigan hair for Rook, you will need to find the bundle for Morrigan eg the strand hair & the npc convo like: livecine/npc_light/templates/namedcharacters(gp)/npclight_morrigan__convo_bundlegenbp_autobundlegen

Load order in the description file: (I havent tested this any other way, but load order do affect the bundles so to be sure set it up like this in both "Bundles" and "Superbundles")

• The NPC/convo bundle first: livecine/npc_light/templates/namedcharacters(gp)/npclight_morrigan__convo_bundlegenbp_autobundlegen

• The hair strand after: characters/actors/morrigan/hair/models/f_har_morrigan_01_strandbindasset_bundlegenbp_autobundlegen

• In some cases (Like Solas), you may need one more bundle such as: livecine/npc/templates/generalpurpose/npc_gp_young_solas_bundlegenbp_autobundlegen

If you are creating a hair swap and not a library, I will refer to that guide on how to use that but I believe the same principle can be applied? Maybe, as you may need more. I've attached my (experimental) version of my library mod. All the bundles are together at the end of "bundles" and "superbundles"