Hi Shelley -- Thanks for your question. I'm not sure where you were getting the information that the Franklin Euro Top is an "8". We actually list as a "Medium" on our softness scale:

https://www.goodbed.com/mattress-model/chattam-wells-franklin-euro-top/

That said, this is not a model for which we've done an in-depth review, so it is possible that the mattress is a bit firmer than what we're listing it at. Alternatively, it could just be that you are looking for something a bit softer than what we call Medium.

In terms of the Harmony Lux lineup, the Diamond Plush Tight Top is one that we've evaluated and that one is exactly a Medium on our softness scale. So if you fond that to be significantly softer than the Franklin, then that would suggest that the Franklin Euro Top is either a Medium-Firm or a Firm.

https://www.goodbed.com/reviews/beautyrest-harmony-lux-mattress-preview/

Re: your question about which is best for you, this is impossible to answer without knowing more about your weight, preferred sleep positions, body shape, preferences, and other factors. That said, I can tell you that every Beautyrest model that has the word "Plush" in its name derives part of its softness from the use of softer coils in the support layer of the mattress. So if you are looking for a combination of softer foam on top with firmer coils underneath, there isn't really a great match for that in the current Harmony lineup. Beautyrest does make that combination readily available in the Black line-up though, so I'd recommend looking there instead.

https://www.goodbed.com/reviews/beautyrest-black-mattress-preview/

I hope that's helpful.