DVD Movies lag
One thing that might help is increasing the VLC DVD cache.
This can be done from Tools -> Preferences (set Show Settings to All) andInput / Codecs -> Access Modules -> DVD with menus (or DVD without menus if you use dvdsimple method for playback) and increase Caching value in MS value to for example to 5000 or to 20000.
Remember to press Save to save VLC settings and restart VLC after that to make sure changes are enabled.
If DVD files from hard drive work better, then check that your DVD drive has DMA enabled (if it is a IDE/ATAPI DVD drive).