I have some old media video files which I'd like to archive. The problem is that these files have different quality and were recorded with different settings (like different volume levels, brightness, etc.) so I'd like to correct this somehow for any uses in future.

One option is to re-code all these files but it would involve losing their current video / sound quality even more and the whole archive will take two times more space (I will need to store original file plus modified one).

The other option would be to create separate media player configs for each of my files (and adjust corresponding settings of the media player) to have similar experience while browsing these files later.

I'm using VLC media player - is that possible to create such separate VLC configs for each video file I have and to "link" these configs to each one video file to let VLC auto-load them when the file starts?

Maybe you could create playlists for those videos and then run vlc with custom parameters? (via a link or a script)

Doesn't VLC have a normaliser? Assuming you just want audible levels, that should at least take care of the audio bit for you.

I went to this link and tried to find out (by Ctrl-F) any parameter to load custom configuration, but couldn't find any - am I blind?

I've found out that VLC's default config data is saved in X:\Users\%username%\Application Data\vlc\vlcrc file.
It has many lines inside, like, for example:

# Audio desynchronization compensation (integer)
#audio-desync=0

and it would be good to find a way to override such options per media file. Incorrect volume level is just one of the problems these files have. :(

Maybe, there's a config parameter right at the end:
--config=<string> use alternate config file

Anyway, my idea was an alternative like running VLC directly with the settings you want:
vlc.exe --audio-desync=0

OK, this seems to be working. I'll try to create separate *.bat files with VLC command line for each media file I have.

One more question - is there some file naming standard which would be recognizable by VLC to search for additional command line parameters?

For example: when you play some movie by clicking on the media file, VLC will look in the same directory for *.srt file with the same name to check if movie subtitles are available and if yes then VLC auto-loads them. Is there something similar for VLC to look for *.??? file to load "additional command line parameters"?

I don't think so, but with a script you could probably accomplish it by yourself.
If you have various files with the same problem, however, you could simply use a (previously created) playlist:
vlc.exe playlist.m3u --params