Hi mollysw,
I’m not sure how long you’ve had your bedinabox mattress but it normally takes little time to go through the initial break in period and for you to adjust to any new sleeping surface and there could be other factors involved in why your mattress feels different from the one you tried in the store. There is more about the break in and adjustment period for memory foam mattresses and some other suggestions that may be helpful in post #2 here although the BIAB mattresses use lower quality/density memory foam than I would normally consider (see post #2 here). Since you’ve already returned it though this is all a moot point.
I would start with the mattress shopping tutorial here which has all the basic information, steps, and guidelines that can help you make the best possible choices … and know how and why to avoid the worst ones.
Dreamfoam is one of the members here which means that I think very highly of them and they compete well with the best in the industry in terms of quality and value and service. I wouldn’t hesitate to purchase any of their mattresses based on the quality of the materials or their “value” but like any mattress purchase the mattress that is “best for you” depends on your confidence about whether it’s a good match for you in terms of PPP (see mattress firmness/comfort levels in post #2 here), and whether you are comfortable with the options you have after a purchase to return, exchange, or make changes to the mattress along with the other parts of your personal value equation that are most important to you compared to the other finalists you are considering.
Yes … latex is the most breathable and “coolest” of all the foam materials but there are also many other factors that can affect the sleeping temperature of a mattress including the mattress protector you use and your sheets and bedding that can be just as important as the type of foam in a mattress. There is more about the different factors that can affect sleeping temperature in post #2 here.
I would keep in mind that there are many options that are in between the two extremes that you are mentioning with either memory foam mattresses or with latex mattresses (or mattresses that use a combination of both materials or even other materials in the comfort layers). The preference about sleeping “in” vs “on” a mattress always depends on the specific design, combination, and firmness of the materials in a mattress and in most cases only your own experience can confirm whether you are in the part of the “in vs on” range that would the best match for your preferences.
If you follow the steps in the tutorial post you will have the best possible chance of finding a mattress that is the best match for you in terms of PPP and is also a great quality and value purchase based on all the criteria that are important to you.
Phoenix