What are Default vs Non-Default? How to choose and install them correctly.

The Sims 4 CC and BTTB will sometimes provide "Non-default" and "Default" options, which function differently despite being named the same.

Default

Custom content with "Default" defined in the file name will override the Maxis original content. It can be a CAS Part or Build item, but in the BTTB installation context, it refers to a Body Mesh.

Installing the BTTB 7 Default Body Mesh will override the Maxis original Body Mesh. This means that every Sim in your save file will have the same Body Mesh, same top, and same bottom. It can be useful if you are tired of selecting a body mesh for each Sim in your town but might not be ideal for uniqueness.

Non-Default

Custom content with "Non-Default" defined in the file name will not override the Maxis original content. It's the standard and recommended way to install BTTB 7 and other CC as well. You will have to manually select the body mesh for each Sim. BTTB 7 provides compatibility with the WickedWhims Body Selector (which is recommended), making it easier to select the body mesh for your Sims.

Conflict

You can install only 1 Default CC per type. E.g., you can install only 1 Default Top body part, 1 Default Bottom body part, etc.

Installing multiple Default Body Meshes will cause a resource ID collision. This typically results in only one of the Default Body Meshes being loaded, and the rest will be ignored. It can be confusing to the player as to which body mesh is being used.

[!IMPORTANT] Installing a Default body is not recommended if you are not familiar with the Default CCs. It's better to use Non-Default body meshes instead.