Hi WCHE00,
Welcome to the Mattress Forum! 
I don’t have any personal experiences with either product, but even if I did, I would keep in mind that there are no “standard” definitions or consensus of opinions for mattress firmness ratings and different manufacturers (and people) can rate mattresses very differently than others so a mattress that one manufacturer (or person) rates as being a specific firmness could be rated very differently by another manufacturer.
Different people can also have very different perceptions of firmness and softness compared to others as well and a mattress that feels firm for one person can feel like “medium” for someone else or even “soft” for someone else (or vice versa) depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress as well (see post #15 here) so different people can also have very different opinions on how two mattresses compare in terms of firmness and some people may rate one mattress as being firmer than another and someone else may rate them the other way around. This is all relative and very subjective and is as much an art as a science.
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation (see post #4 here) with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (resilience, firmness, etc.) and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
When “evaluating” any mattress, I would always make sure that you find out the information listed here so you can compare the quality of the materials and components to the durability guidelines here to make sure there are no lower quality materials or weak links in a mattress that would be a cause for concern relative to the durability and useful life of a mattress before making any purchase.
The Nolah is comprised of:
2" 2.75 lb polyfoam
1" 4 lb Avena polyfoam
7" 1.8 lb polyfoam support core
This product would raise no “red flags” for someone in a more “normal” BMI range, but I would advise a slight caution for someone in a higher BMI range (30+).
The Leesa is comprised of:
2" 3.65 lb Avena polyfoam (20-26 IFD)
2" 3lb Memory foam (9 IFD)
6" Polyfoam 1.8 lb density (32-38 IFD)
The Avena polyfoam is good quality, but I would be cautious because of the 2" of 3 lb memory foam in the comfort layers which could be a weak link in the mattress in terms of durability.
Phoenix