Hi Maxcook64,
Your own careful and objective testing is always the most reliable way to know whether a mattress is a good match in terms of PPP and I would make sure you read all the testing guidelines in the tutorial post. Good testing will give you the highest odds of success.
There is really no way to predict this on an individual basis because there are so many factors that combine together that are involved in sleeping temperature besides just the type of foam used in a mattress (see post #2 here). Memory foam (or gel memory foam) in general tends to sleep warmer than other types of materials or foams but if you are OK on the Cloud Luxe you will probably be OK on the Rhapsody as well. The Cloud Luxe uses 4 lb memory foam which is more breathable than higher density memory foam but the Rhapsody is also firmer which will also be cooler than softer mattresses where you sink into and are surrounded and insulated by the memory foam more. Some of the other factors involved in sleeping temperature (your mattress protector and bedding) can also make a significant difference in temperature (in some cases more than the difference between the mattresses).
With your wife’s lower weight she will likely do better with a softer mattress than you so there may be some compromise between you but it will also depend on her sleeping positions. Side sleepers generally need thicker/softer comfort layers to relieve pressure than back or stomach sleepers. The general rule is to make sure you test the mattress in all your sleeping positions and then choose a mattress that is “just soft enough” to relieve pressure points in your most pressure prone position so it will have a lower risk of producing the pain and discomfort in your lower back that can go with the alignment issues that are the result of a mattress that is too soft. The Allura uses the higher density 7 lb memory foam which is more supportive and would be closer to the Cloud Luxe (especially in the softer version) than the Rhapsody which would be a much larger step up in terms of firmness.
It may also be worth considering some of the Cloud line that uses thinner layers of memory foam (such as the Supreme or Select) which are a little firmer but are still in the soft range and which would also reduce the risk of alignment issues.
Phoenix