Go with the peat based mix. I would stay away from woods dirt as it already contains all of the fungi necessary to kill off the whole bed. Also, I've learned that at times it becomes necessary to empty the beds and start over. So, pick a mix you can replicate, and one that you can use elsewhere (your garden and flower beds) when it leaves your ginseng beds.
I use treated 2x8s and make the beds four feet wide and sixteen feet long. In each bed i put six to eight large bales of red Canadian peat. I mix the peat with mason sand. I also put a couple inches of sand on the bottom of the bed before I put in the peat/sand mix. Mix the top layer well and the bed will begin disease free.
I use the red peat because of its acidic qualities. Likewise, if I am going to leave a bed long-term, I sometimes mix in a few bags of shreaded hardwood mulch. The wood is acidic as well. I don't add anything other than maybe gypsum (this adds calcium without raising the pH like lime does). Never fertilize these beds or you will find yourself in an everlasting fight with disease.
This mix will work well for either seeds or rootlets. Just make sure it is uniformily moist or the seed and rootlets may dry out. (I would recommend making and filling the beds now, and planting them in the fall. Water them good at first, then let them reach a natural state of moisture.