Are the old BSN DAO mods will available?

BSN is gone completely. All gone. The mods are available at other websites.

Here is a helpful article on how to retrieve the DLC.

The mods hosted on the site are scattered now. You may want to employ your Google-Fu if you are hunting for a specific mod.

To get you started, tmp7704's dwarf proportions fix may be found here. For others, I highly recommend starting at the Dragon Age Nexus.

Some BSN-projects mods are on the Nexus. Some are elsewhere, such as tmp7704's (essential IMO) mods, which are all here. Many, regrettably, are not currently available.

A good resource for locating former BSN content is the community effort, Bioware Continuity Network.

While you can place everything in the override root, it's a really bad idea, IMO, as it makes it very difficult to know what mod any file came from. 'Tis much better to keep them separated in mod-specific folders.

And since there can only be one chargenmorphcfg.xml file in override, if you are installing multiple cosmetic mods, you'll need to merge the data from all the XMLs. The easiest way to do that is to place each XML in the same folder as the mod's files, and use the Dragon Age CharGenMorphCompiler utility.