Hi skrell,
There are some general guidelines on how to select a topper in post #8 here.
Generally:
If the mattress needs just a “touch to a little” extra softness or a softer “surface feel” … then a 1" topper is usually enough.
If you need a little to a fair bit of extra softness and pressure relief … then a 2" topper would be in the average range.
If you need a fair bit to a lot of extra softness then a 3" topper would probably be the best choice.
Heavier weights generally do better with firmer and thicker toppers.
Lighter weights generally do best with softer and thinner toppers.
Phoenix