Yes if you use Video Decoder DXVA, if you have an NVidia (you can enable Cuvid).
LAV is composed of Source Splitter + Audio + Video codec. But you can use another codec like PDVD11/MPC Video.
But with LAV Splitter, you can have Forced subtitle
Since I am using the LAV splitter the mkv files are stuttering in the first secons file playing. With haali splitter there was no stuttering. Is this normal?
Nope, this is not normal, try to play the same file with GraphStudio, if you have it, does not stutter there, there is some misconfiguration in MP. You can try to play in MPC-HC player, or VLC. If it plays normally in those players, look at the config in MP.