Hi Aza,
Just as a “FYI” … if your latex mattress was a Sealy (such as the old Springfree line) then you have most likely been sleeping on polyfoam comfort layers not latex even though they sell them as “latex” mattresses. The weak link of most mattresses are the layers near the top which is where it’s most important to have good quality materials.
You can read a bit more about the Optimum lineup in post #48 here. As you can see … the Radiance uses the lower quality base foam and has 2" of lower density gelfoam along with 2" of memory foam of unknown density (not a single retailer I have talked with has been able to find out the quality/density of the memory foam layers although it is quite likely on the low side). In other words you are dealing with a mattress that is impossible to assess the overall quality but where the base materials are low quality, the gel foam is lower quality and the regular memory foam quality is completely unknown.
The iComfort Savant (the more detailed analysis of the iComfort lineup is in post #11 here for others who may be reading this) also uses some low quality foams in the critical comfort layers and also has a low quality support layer and the gel foam is also lower quality … but at least the KoolComfort density is known (5 lbs) and is good quality. This is the softest of the three choices and would probably be the most risky in terms of alignment.
The Tempurpedic cloud (assuming you are referring to the basic cloud model which is now being cleared out) uses 1.2" of mid quality 4 lb softer memory foam and then 1.6" of high quality 5.3 lb memory foam and has a higher quality polyfoam base layer as well (@2.2 lbs or higher). The memory foam is also thinner with this mattress which for some people may be “safer” in terms of alignment but also may not be as comfortable (pressure relieving) as either the Optimum or the Savant. Your lighter weight may make this more suitable (depending on the position you normally sleep in) and the overall quality here is better than the other two options but the “value” is just as poor because there is less material in the mattress.
So overall … I would generally tend to avoid all 3 of these because they all have poor value (for different reasons) and I would not want to be forced into making a decision between them. If I had to choose though … and since none of them are good value anyway … I would choose based on which one best met your needs and preferences in terms of PPP (Pressure relief, Posture and alignment, and Personal preferences). In other words the one that was most “comfortable” (pressure relieving), had the best support (kept your spine in neutral alignment in all your sleeping positions) and also provided the other features that were most important to you (such as sleeping temperature and other preferences listed in post #2 here). Since “value” isn’t an issue in this case … I would let your body make the choice.
In terms of sleeping temperature … then the Optimum and the Serta may be a little cooler than the Tempurpedic although you mentioned this wasn’t as important to you.
This is not a choice I would want to make!
Phoenix