Some thoughts:
Do not install Mplayer as this is obsolete and the Mplayer service no longer exists.
Not really an option during setup. Mplayer is automatically installed along with the game when installing from game CD, so it must be uninstalled afterwards. Manually extracting files from the installer and patch installer is also an option to avoid Mplayer. Also, some people have problems running the installer because they have certain program running in the background that blocks it from starting. Technically, both installer and the problematic program is flawed. I think I wrote about this the last time someone asked for help installing Drakan.
There is also the option to use DGvoodoo during install which emulates a 3DFX Voodoo2 card and may work better for some users with certain video cards. I found it was not needed running on Nvidia GTX970 hardware.
This only applies to Glide portion of dgVoodoo, not DirectX portion, which is the one suitable for Drakan. By translating DIrectDraw/Direct3D 6 rendering calls to modern equivalents, it generally improves performance on newer graphics hardware (and decreases it on older) and provides better integration with the operating system due to bugs in interaction between legacy and modern components. For example, on Windows 7 and Vista, running Drakan in fullscreen mode results in programs' thumbnails used for alt-tab and taskbar preview to get lost. On Windows 8/8.1/10, there is a 3 second delay when switching away from the game if it's in fullscreen and runs at the same resolution/refresh rate as the desktop due to a bug in sync mechanism between DirectDraw and DWM. There is a good chance that preventing access to the handle to DWM_DX_FULLSCREEN_TRANSITION event in dwm.exe using Process Hacker works around the bug without negative side effects, although the more correct fix is part of experimental version of
DDrawCompat, which is a bit of an overkill for Drakan.
Either way, it's best to test both with and without dgVoodoo to see what works best.
There is also the 10th anniversary patch which fixes some issues and improves performance but this cannot be used to play the game online without the community patch.
It's actually the opposite; it kills the performance and introduces extra issues. Also,
its suggested configuration turns Drakan into some sort of abstract art mess or however you want to call it.
It can be used while playing online as long as you don't overwrite your Drakan.exe by running its installer, which opens easily with 7-Zip.
Also you may get a crash when browsing the servers. This appears to be the game trying to connect to a non existent server. If this happens try deleting the obsolete servers from your servers.txt file.
This was fixed in AiO Patch. And it actually crashed if it contacted the machine which was online - connected to the internet - but didn't have Drakan server running and therefore connection attempt failed with WSAECONNREFUSED error code on the sockets API side. Nothing happened if nothing appeared behind target IP address. There is still one unresolved unrelated bug that sometimes crashes the game when ESCaping from the Join Game menu.