Hi david_a,
You certainly made a great quality choice and your mattress uses high quality materials that would be suitable for your weight range in terms of durability but the most important part of any mattress purchase is PPP (Posture and alignment, Pressure relief, and your Personal preferences) and the only way to know whether any mattress is a good “match” for your body type and sleeping style will be based on your own careful testing or personal experience.
The medium firmness would normally be “in the range” that had the best chance of success and would be most likely to be suitable for you based on “averages” but unfortunately each person is unique and not everyone fits inside the averages of other people even if they have a similar body type and sleeping style.
If I was in your shoes I would probably try your mattress without the topper for a few weeks (if you haven’t already) to give the mattress a chance to break in and for you to adjust to a sleeping surface that is different from what you are used to (see post #3 here) because the comfort layers in the mattress may be softer than your firm topper and your topper could be part of the cause of your discomfort. If you are experiencing pressure points in your shoulders then it’s also possible that your “symptoms” are a pillow issue rather than a mattress issue.
While it’s not possible to “diagnose” mattress comfort issues on a forum with any certainty because there are too many unique unknowns, variables, and complexities involved that can affect how each person sleeps on a mattress in terms of “comfort” and PPP (Posture and alignment, Pressure relief, and your Personal preferences) or any “symptoms” they experience … there is more about the most common symptoms that people may experience when they sleep on a mattress and the most likely (although not the only) reasons for them in post #2 here that may be helpful.
If your mattress is too firm then the information in post #2 here may also be helpful and I would make sure that you have a suitable support system under your mattress and also confirm that any mattress pad or mattress protector you are using isn’t contributing to the issues or “symptoms” you are experiencing as well.
Assuming that the materials in a mattress you are considering are durable enough for your body type and meet the quality/durability guidelines here (which they do) … the choice between different types and combinations of materials and components or different types of mattresses are more of a preference and a budget choice than a “better/worse” choice (see this article).
There is also more about the pros and cons of memory foam vs latex in post #2 here but the best way to know which type of material you tend to prefer is based on testing a range of mattress in different firmness levels in each category to see if you can identify any “pattern” in your preferences.
Every category of mattresses can include hundreds (or thousands) of different mattresses with different designs and different firmness levels so each category will generally include some mattresses that you will sleep well on and other mattresses that use the same type of materials and are in the same category that may be unsuitable for you to sleep on (regardless of which materials are used in the mattress).
In other words … how well the specific design of a mattress “matches” your body type and sleeping style in terms of Posture/alignment and Pressure relief/comfort is generally more important than the type of materials themselves (which is more of a preference based on the “feel” and response of different materials). Like most things … different people can have very different preferences.
Phoenix