I am just starting out and there is such an amazing selection of music on the CDLC database. Although when I start it up its at 100% from the start of the song.

 

Does any CDLC work like the official music with the dynamic difficulty?

of course they do . Just watch out for CDLC with DD.

Seems like you tried out Customs with NDD (No Dynamic Difficulty).

I also have experienced some CDLC that are DD, but start at 100%.  If they actually are DD songs then you can go into Riff Repeater, select the whole song, drop the difficulty down to an appropriate level, then resume the song.  From that point it should increase your difficulty just like official content.