As far as I know there are two types of Murphy beds, the ones that tilt up in one piece and the ones that fold. If comfort is your concern the later ones will be probably not for you. The ridge where they fold should be about your butt/thigh height when laying down so should be barely if any noticeable. In either case you can get aftermarket mattress to meet your comfort and firmness preferences.
Keep in mind there will be certain limitations with Murphy bed when it comes to mattress thickness. You will need to consider how thick and heavy your bed sheets and pillows are to make sure you can still fold/fit them when tilted up. Heavy mattress, sheets, comforter etc will add up to a lot of weight that you will have to lift every time you fold your bed - may end up being a workout especially if you're smaller posture.
I personally prefer to have a solid division with doors between living space and bed for all privacy, smells and sleep disturbance limitation.
2014 Toyota Sequoia
2018 Sunset 239BH