Hi cmsivley,
This is a very common preference – having a “firmer” base mattress and then using a topper to achieve extra comfort. It’s actually the type of system that Luma Sleep uses with their latex hybrid mattress you mentioned in your last post.
No necessarily. It would depend upon the configuration and layers within your base mattress, and the type of topper (thickness, material used, ILD) that you would be placing upon that base mattress.
There is more information about choosing a topper in post #2 here and the topper guidelines it links to which along with a conversation with a reliable and knowledgeable supplier (that can provide you with good information about how their toppers compare to each other or to other toppers they are familiar with that are available on the market) can help you use your sleeping experience as a reference point and guideline to help you choose the type, thickness, and firmness for a topper that has the least possible risk and the best chance for success.
Phoenix