I am creating models in Blender for a game in Unreal Engine 4. What output file format is the best and I can use for this for commercial purposes?
Most people use FBX when exporting to UE4 – you'll find a lot of information over at the UE4 Wiki in the Blender Section
Personally the only issues I've dealt with myself are:
- Importing meshes with millions of polygons (something you should not really do in a game engine anyway) takes a few minutes.
- Applying modifiers before exporting is a good idea as I've sometimes had some meshes in the .fbx missing when importing
There are also a few live-streams from UE4 that are archived on YouTube, for example: https://www.youtube.com/watch?v=KDP7GHFtAtE
The best output format is the one recommended by the game developer. There is nothing from the Blender foundation that would affect use for commercial purposes, but elements of the game may be covered by other intellectual property considerations. For example, it is possible that the game developer trademarked elements of the game which could be infringed by the content you create in Blender. Consulting the game developer would be the best source of info on what might, or might not be infringing.