Yes and no. GPU gaming performance deals with probably a very small subset of the files. There's a saying that 10% of the code of a program runs 90% of time. Some studies actually say it's 5%/95%. Companies like AMD could also have different teams for different parts of the driver kit. For example, there could be one team that works on the rasterization part, another that works on the Radeon Control Panel
However, over-bloat can be an indication that they aren't taking the time to polish things.
The AMD driver for 2 GPUs being around the size of the big set actually makes sense. The UI for the new drivers looks the same, and the bundled software is probably making up the bulk of the package.
AMDSplashScreen.exe is just a splash screen, and it's 10 MB. QT5's DLLs (Qt5*.dll) are 110 MB on the C:\Program Files\AMD\CNext\CNext folder. C:\Program Files\AMD\CNext... looks like 381 MB of the drivers is mostly the control panel UI and features like Twitch integration. There might be things like GPU-accelerated video decoding going on, but it's hard to tell just by looking at the folder
100 MB for what looks like a copy of the installer that's probably mostly the base-bones functionality.
40 MB on localization itself (also CNext folder)
ffmpeg is there. avcodec-58.dll is around 30 MB. 110 MB for qt5*.dll and 40 MB for localization. There's 180 MB right there. There's a few ffmpeg files that nickel-and-dime the size up, pretty significantly
This PC has been upgraded a lot, so there's a chance that these could be old file.