Hi jasonsmith.
Yes! There have been a number of other members who’ve gone the topper + firm mattress route. If I’m remembering correctly, this was most recently discussed in this topic. You may find some useful information in the conversation there.
A mattress that is adequate for your BMI, sleeping positions, and activities on the mattress shouldn’t be developing body impressions any time soon. You should be able to get the full length of life out of a quality, appropriate mattress.
Ultimately, with regards to soft or medium, I would suggest reaching out to each of the manufacturers and explaining your plans to them, as well as your BMI and sleeping positions, so they can help guide you (especially if you may be considering 4" instead of 2"). They will be the best resources with regards to their own products and are experts in this field.
NikkiTMU