There is only one thing I couldn't find how to configure: subtitles position...
Perhaps this can be of interest to somebody.
I stumbled on a bug (can somebody confirm this?) and looked for a solution and found one that solved the internal/external subs issues.
I managed to setup MP v1.02 in such a way with MPC-HC and DirectVobSub that it currently plays anything with internal and external (or both) subtitles with CUDA ('Compute Unified Device Architecture', improved architecture and better than DXVA) enabled (of course CUDA only if the movie format allows hardware acceleration).
[Alleged BUG] In the MP Video configuration I finally needed to choose DirectVobSub over MPC-HC because MPC-HC has subtitle synchronisation issues with 1080p MKV's.
I tested it for 5 hours with different MKV's in different setup's (internal/external/mix subs, vobsub enabled/disabled (which shouldn't matter), etc...) but each time the subtitles were displayed 1-3 seconds too early (in case of internal subs) or too late (external subs in combination with a MKV with and without internal subs).
And if you changed the subtitle language during play-time the delay would change randomly.[/BUG]