DVD encoding, what is best method?

I already have basic dvd authoring and burning programs so not looking to hear get ConvertXtoDVD, which I already have and the only dvd burning software I could get to work with .mkv format, but most of my videos are .mp4/avc, .avi, .wmv, and although somewhat knowledgeable about this I need more info from experts. I have bluray movies and have already converted them into the before mentioned formats and all look very good on the pc but lose quality converting to mpeg/.vob. I've read about HC Encoder and something about ECC encoder. I have AVStoDVD open source program that allows non .avs to convert, naming them .avs inside HC (except .mkv), but trying directly to use HC Encoder it wont even allow me to choose a non .avs. This program works except for .mkv and using COnvertX right now for the .mkv and seems to be doing fine. Tell me more about what to use for the absoloutely best quality onto a dvd or am I already using the best with HC Encoder via AVStoDVD, although somehow tricking HC into thinking it's something it's not (.avs). Tell me what you use even if complicated or is expensive software I am willing to buy if needed. Need the best! Thanks in advance