Sit on your bike and look at the angle your feet hang at, you want your cleats to be straight in the peddles with your feet in a reasonably natural position for you, otherwise you’ll introduce knee strain.
If you do feel any pain in your knees at all you’ll need to fiddle with the angle. IIRC as a general rule, pain on the inside means your heels are out too much, pain on the outside means they are in too much. Adjust your cleats accordingly.
In terms of the backwards/forewords position, whatever your preference is. Personally like mine as far back as possible, as I find it more stable on the decants. Some will claim moving them foreword will help you get more power out of them though.
Run them as loose as they’ll go initially, but when you ride make sure you have a multitool so you can tighten them as you get used to them. On Shimano SPDs each notch makes a pretty minimal difference, so I’d wind them in two clicks at a time.
