VRAM, mips, and not guessing BC from a blog title
Unity
The editor can ingest PNG and crunch. Pre-baking helps constrained platforms. Still set sRGB versus linear correctly.
Unreal
Streaming and BC choices are project settings. A browser encode is an input, not a cooked .uasset.
Legacy Source/Cry
Those pipelines are picky about sizes and faces. Read the mod wiki, then encode.