Another good book is Whole Grains for Modern Meals by Maria Speck.

wheatberries can be cooked and frozen as well; that's what i do>>just grab a bit from a bag of frozen ,and add it to rice/other grains at the end of its cooking. Trader Joes also sells a frozen Rice Medley w/ some tasty chewy grains.

You could use farro or spelt in place of hybridized wheat berries. I don't know if it matters to you, but quinoa--like buckwheat- is not a true grain. Quinoa is a the seed of a plant related to spinach.

Soft and hard are references to the grain's milling quality, related to protein / gluten content. Either will work just fine for cooking whole. You'll find some difference between white and red wheat however, the red having more flavor.

I don't think that matters until you get to flour and baking. At the grain point, it's pretty much the same, AFAIK. If you want an easy way to add grains as salads/sides, have you tried Kashi pilaf - six or seven grains plus sesame seeds? No, I don't work for them, but I've been using that for years and years. It's gotten hard to find in my area, so I buy the individual grains, whatever I find that looks good, and make my own mix -- good way to avoid gluten if you need to. It cooks up easily in a rice cooker -- just add your herbs and spices to the grains and cook with broth or water. I serve it hot as a pilaf, cold as a Tabbouleh or other grain salad, stuff veggies with it, and even use it as in my veggie burgers. The mix of grains tastes great, nutty and chewy-crunchy, so most folks, even kids, like them. Every once in a while I'll sprout the whole Megillah and put in in my bread dough, too.
There, probably more than you wanted to know based on your question. ;)

I usually get hard wheatberries and boil for about an hour to soften. I don't soak, just clean and boil. They are wonderful!