The current custom armors method doesn't support animated and emissive textures.
To create animated or/and emissive textures you have to use the old method shown here (uses shaders).
HD armor textures
I do not advice to use HD textures since this is a blocky game, but can create HD high resolution, but make sure they have the same proportions of the original vanilla armors layers textures.
Size must be a power of 2, for example: 64x32, 128x64, 256x128, 512x256.
Multi-version compatibility
This custom armors feature is only available on 1.21.2 and greater clients and servers.
There is a simple solution if your server uses ViaVersion or similar, but has some downsides and it should be considered as a legacy feature. I discourage using that feature.
You have to create both properties equipments and armors_rendering.
armors_rendering is the old method (uses a custom shader).
equipments is the new method (uses the vanilla equipment attribute).
You have to set material to LEATHER, for each piece, in this case LEATHER_CHESTPLATE.
You then have to set the equipment.legacy_armor_rendering_id and equipment.id to the previously created properties.
Extra: Custom 3D helmet
Minecraft 1.21.1 and lower do not support helmets (DIAMOND_HELMET, LEATHER_HELMET etc.) to create 3D hats due to a Minecraft limitation I cannot fix.
In this case, to support legacy clients too, you must use a different material like PAPER and use the hatbehaviour instead.
This setting allows you to append the new equipment setting and use the old shader method + the new method at the same time, so old clients will still see armors even if they are not on 1.21.2+.
Mode 2
This option will convert the armors completely to use the new equipment tag. Note that old clients won't see the armor anymore (older than 1.21.2).