The Dev version adds a good amount of new stuff (which I don't want to tell here, as it could be seen as spoilers). Not sure what you would count as "experimental mechanics", but there is definitely something to be found by doing some exploration. Be careful though: as a beta version, it isn't finished (most of the new stuff lacks description, there might be a few bugs, etc).
As for the skin pack, simply use it alongside the main mod and change the game version its mod_info.json asks for. If that *still* don't work, simply copy/paste the sprites from the skin mod's folder into the main mod's ship folder. I doubt it'll be needed though.