Hi jkxs,
Welcome to the Mattress Forum! 
[quote]I am hoping to get some suggestions on potential mattresses that may work for me. I admit that I do not know anything about mattresses other than what I read on the tutorial and thought that it would be a better idea for me to get suggestions. Thank you for taking the time to read my thread! Please feel free to ask me any questions and I apologize if I made any mistakes.
Format copied from another thread:
Height: 6’2"
Weight: 170 lb
Size: Currently Queen, but looking to buy a Full sized mattress
Usually sleep on back, or side and prefer cool mattresses
Location: Currently Fairfax, VA but will be living in Harrisonburg, VA when school starts in late August
Budget: Under $600
Mattress/topper picture album: here
Current Mattress: Simmons (not sure what model - see tag?) - innersprings units covered with 100% urethane foam
Sleep Innovations 3" Polyurethane Foam (Memory foam?) Mattress Topper
Not sure what my frame is model-wise, but it is wooden and has 12 slats (see album) [/quote]
Unfortunately I don’t have any specific suggestions 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 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 would be the best “match” for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) or how a mattress will “feel” to you based on specs (either yours or a mattress) or “theory at a distance” that can possibly be more accurate than your own careful testing (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).
I can certainly help you to narrow down your options, help you focus on better quality/value choices that are available to you either locally or online, help you identify any lower quality materials or weak links in a mattress you may be considering, act as a fact check, answer any questions you may have along the way that I am able to help with, and help with “how” to choose but only you can decide which specific mattress is the best match for you in terms of PPP or all the other parts of your personal value equation that are most important to you.
As I mentioned in the post you linked I would avoid any mattress with 2.5" of 3 lb memory foam which would be a weak link in the mattress in terms of durability and the useful life of the mattress. There are certainly many better and more durable options available.
I would also be very cautious about about using other people’s experiences or reviews on a mattress (either positive or negative) or “amalgamated review sites” as a reliable source of information or guidance about how you will feel on the same mattress or how suitable or how durable a mattress may be for you and in many if not most cases they can be more misleading than helpful because a mattress that would be a perfect choice for one person or even a group of people may be completely unsuitable for someone else to sleep on (see post #13 here).
Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here (which is the one you’ve already read and linked in your post) which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability, durability, and value.
If you are looking at Amazon or any other online options then you can use these posts as a reference source to help you decide whether any particular mattress would be worth considering.
If you are limited to lower budget ranges yet then some of the better lower budget online options I’m aware of are listed in post #4 here and the posts it also links to (which is in the same topic that you also linked in your post).
The better local options or possibilities I’m aware of in and around the Washington, DC area including Fairfax (and subject to the quality/value guidelines I linked) are listed in post #2 here. The forum list for the areas in and around Charlottesville/Lynchburg/Waynesboro (which would include Harrisonburg) are listed in post #3 here.
Based on your picture it looks like your platform bed would be suitable for a foam mattress without needing a foundation as long as it’s the right size and has a firm, flat, and non flexing support surface and it doesn’t have any soft spots or sagging. With a full size you can get away without center support but if you purchase a queen then your support system would also need good center support to the floor.
Phoenix