Hi jsteele212,
There is more in post #13 here about the most important parts of the “value” of a mattress purchase and the most important of all of them is choosing a mattress that is suitable for you in terms of PPP. Everything else would come after this because if a mattress or mattress/topper combination isn’t suitable for you to sleep on then it would have little value to you regardless of durability or price.
So you will need to assess the risk involved with each option and how confident you are that each of them will be a suitable choice. This will also depend on your confidence that careful and objective testing will do a good job of predicting your sleeping experience. When you aren’t confident in a choice then the options you have afterwards will be a much more significant part of the “value” of your choice and the risks involved.
IMO … because you have a reference point with your current mattress and a 3" latex topper that seems to indicate that it is “close” … it seems to me that a slightly thinner topper would have a good chance of success and this would be one of your least risky options in terms of suitability and PPP.
If you are confident in your testing … then option #2 would also be a good choice in terms of suitability. If you aren’t … then you would have limited options available afterwards because you can’t make another exchange so it would become the most risky choice … especially if you chose a mattress that was too soft because it’s not really possible to “firm up” a mattress that is too soft expect partially or temporarily.
Option #3 has more variables involved than the other two so unless you can bring your topper into the showroom and test the combination in person AND you are confident in your testing it would seem to me to be the riskiest choice. If you are confident in your testing and you bring the topper into the showroom then the risks would be the same as #2.
Outside of suitability … there are also an additional set of risks that are related to durability but these would be secondary to suitability.
Assuming for the sake of this part of the comparison that you would make an equally suitable choice with each of them … I would say that option #3 would likely be the most durable followed by option #1. Neither of these are likely to have any weak links in their design (especially if you flip and rotate the base mattress). With option #2 being only one sided (I misread your comments and thought you were looking at the Orthopedic Eurotop in my last reply) whether I would consider this at all would depend entirely on the specifics of the density of the foam layers inside it. If you find out the density of all the layers and it turns out that there are some obvious weak links in the mattress based on the guidelines here … then no matter how suitable it was I would avoid it because of the higher risk of premature foam softening and breakdown and the potential early loss of comfort and support.
Trimming a 3" topper down to 2" would be very difficult and “risky” without specialized equipment but there are some suggestions in post #2 here that may be helpful.
Phoenix