Hi d3adrock,
I would suggest the testing guidelines in step 4 of the mattress shopping tutorial.
The most common cause of lower back pain is a mattress that is too soft (either comfort layers that are too thick/soft or support layers that are too soft) and if a mattress is too soft “for you” and your hips/pelvis are sinking into the mattress too deeply then the odds are certainly higher that you could experience lower back pain or discomfort. Having said that … not everyone fits inside the “averages” of other people that have a similar body type and sleeping style so your own careful testing or personal sleeping experience and lack of any symptoms or discomfort is the most reliable way to know whether any specific mattress is a good “match” for you in terms of PPP (Posture and alignment, Pressure relief, and your Personal preferences) because each person is different.
There is more about what I call primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support/alignment” and “comfort/pressure relief” and “feel” and how they interact together relative to different body types and sleeping positions.
Phoenix