Why are the display plates available from the start of the game without researching anything?

DisplayPlatesForked does not define any research for its items, so there is no technology to gate them behind. Nullius normally hides items like this to keep them out of the way, which is part of what breaks them in the first place. Restoring visibility without also adding new research entries means they show up immediately. Adding a proper Nullius-compatible technology unlock is planned but is a more involved change.

Do I need DisplayPlatesForkedTweaks or SchallCircuitGroup?

No, it's just an optional organization mod. If you have SchallCircuitGroup installed, the plates will automatically move to the Circuit tab. Other mods exist to move Display Plates to the Circuit group that Schall makes such as DisplayPlatesForkedTweaks, but that functionality is already covered here. No conflicts will occur if you happen to install mods like DisplayPlatesForkedTweaks, but it won't do anything this mod is not already doing.

Are there any other mods this is compatible with?

This mod only accounts for the required Nullius and DisplayPlatesForked mods and the optional SchallCircuitGroup and adjusts accordingly. Any other mods that reorganize the crafting menu should be unaffected since the mod only moves plates into a subgroup when it knows that subgroup exists. If a mod you use causes issues, open a discussion thread and I'll take a look.

Will this work mid-save?

Yes. The changes are all data-stage patches applied at load time, so adding or removing this mod does not touch your save file. Items already placed in the world will persist regardless.

Why are the ingredient amounts unchanged from the originals?

The quantities (1, 4, and 9 by size) come directly from DisplayPlatesForked's original recipes. Only the materials were swapped to fit what Nullius provides. Whether those amounts feel right against Nullius's economy is worth checking in your own playthrough. If they feel off, open a discussion thread and share your thoughts, I'm always open to feedback and suggestions for balancing the recipes.

Why were the materials and colors of some of the plates changed?

The Iron and Steel plates both kept their original textures since the visuals still make sense for their new names. The copper plates were the exception. A copper texture on something called a Plastic Display Plate was a bit jarring, so those got recolored. Plastic is a "dirty white", so the palette shifted greyer as a side effect of matching the actual materials, not as a deliberate design choice. If you have ideas for making the three variants more visually distinct while staying true to the Nullius materials, open a discussion thread. Graphics suggestions are welcome and I'm happy to any within my personal abilities.