Hi jjen,
Welcome to the Mattress Forum! 
I’m glad you found us as well.
The sensation of being “in” a mattress versus being “on” is a result of all of the materials contained within a mattress, but you are very correct that the uppermost layers (the memory foam versus the latex that you mentioned) will have the most impact. Softer foams (lower ILDs) will allow you to “sink in” more, and foams with more resiliency (what some people describe as “push back”) return more energy versus those with more “energy dispersing” characteristics, such as memory foam. Memory foam will tend to allow you to “sink in” more than latex, although a plush latex in a thick enough layer will also allow a bit of “sinking in”, but it will be easier to reposition upon. You’d probably want to make sure that whatever you choose has enough surface firmness, combined with good deep support for maintaining proper alignment.
There is more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel” that may be useful as well. A mattress using an innerspring, all-latex core, or a polyfoam core can all provide good “deep support”.
Many of the new innerspring “hybrid” mattresses are using innerspring units with a perimeter of firmer springs for edge reinforcement, versus a polyfoam edge system, and they are meant to be adjustable bed friendly. But you’d always want to confirm beforehand with any manufacturer/retailer you are considering.
While I can certainly help with “how” to choose … It’s not possible to make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort”, firmness, or PPP (Posture and alignment, Pressure relief, and your own Personal preferences) or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
There are hundreds of “hybrid” offerings available nationally, but if you’re considering shopping online you may wish to start your search by using the experience and expertise of the members listed in post #21 here who are all very experienced and knowledgeable and specialize in providing the type of help and guidance on the phone that can help you make good choices. There is a wide range of hybrid options included in the choices there and I believe that all of them compete well with the best in the industry in terms of their quality, value, service, and transparency. You’ll also want to have a phone conversation with any business you’re considering, and make sure that you have complete details of the componentry within the mattress (following the guidelines as outlined in the mattress shopping tutorial here) and probably choose something that eschews memory foam in the upper layers and uses polyfoam or latex, and is in the generally-described “medium” to “medium-firm” level of comfort, based upon your stated preference. Of course, comfort terminology isn’t standardized, and only through your own personal testing will you be able to determine if what you’re considering meets with your desires.
If you have specific questions about any mattress you’re researching, feel free to post back here in this thread and I’ll do my best to be assistive.
Phoenix