Panel filesize limit by filetype in blueprint

is it possible to set the filesize limit by filetype not for all files? i would like to have 300kb for images but allow 5mb mp3 files.

No, that is currently not possible. You can only set the general limit for all types.
I have created a feature request here.

It’s a really good idea. In general I think we need more flexibility for accepting, denying files.