To keep my spine/neck properly aligned and avoid waking up tired/achy, which type/firmness/thickness of mattress and pillow should i be using? there are so many choices that it's hard to tell which is best for good sleep & back/neck support.

Don't try too hard: Everyone is different, but generally, I would recommend a firmer mattress with a pillow top, or memory foam. Don't use too many or too large pillows as this could put the neck too far from neutral alignment. During the night, your body will find comfortable positions, so just let it. The best support of the back and neck come from postural exercises while awake! I recommend yin yoga also!!