It seems that Virtual PC additions is different, but compatible, between versions.
Quote from Virtual PC 2.1.1 with Win98 Extras folder:
"If you install a version of Windows 3.11, you may want to install VPC Mac integration drivers. The Mac integration installers for Windows 3.11 are included on the Virtual PC Installer CD-ROM (version 1.0.1 only, it is NOT included on the Virtual PC 2.1.1 CD)"
And it seems that additions of later Virtual PC version depends bundled OS, maybe Connectix thinks that people buy many Virtual PC:s with different OS.
So I think we should make ultimate collection of additions for different operating systems.
You can find easily Win95-XP additions (Except WinNT) from Macintoshgarden, but I think there was also Virtual PC with Linux (and later Redhat Linux), OS/2, WinNT, OpenStep. And I looking for Extras folder of them. Or if somebody have additions files from Connectix ftp-server (I think those files was available when Virtual PC 3 was new).
EDIT: and there might be newer additions for Win95-XP that there is Macintoshgarden right now, because it seems that there was separete Virtual PC 3.0 with Win95:
https://www.ebay.ca/itm/Virtual-PC-3-0-w-Windows-95-Open-Retail-Box-Sealed-Contents-Connectix/124530306054