Hi Jdavis,
While all foam materials will soften and impress to some degree … latex will do this more slowly and less than other materials. A topper will also contour to the layers below it however which is why a topper is unlikely to fix a mattress that is too soft or has developed soft spots. while it’s always possible that you have a defective topper (and Latex International seems to have more of these than other latex manufacturers over the past few years) … the odds are higher that what is under your topper is the most likely cause of your soft spots and hills and valleys. You can read more about this and some possible solutions and things to check for in post #4 here. you can also test to see if the topper is part of the issue by lying it on a flat surface like the floor and putting a straight edge or running a string across the mattress over any impressions to measure the depth of any impressions.
With neck issues there is also a strong possibility that it may be connect to your pillow and how well it is keeping your head and neck in good alignment and looking underneath the area of the actual symptom is a more likely possibility.
If the topper does turn out to be defective then you should be able to replace it under warranty.
This would be a good option if your mattress was still in very good condition and there were no soft spots or dips in the mattress itself. if your mattress has several inches of softer polyfoam in the comfort layers then the odds are good that it may not be the best candidate for a topper.
All your other options (#2 and #3) appear to be good ones depending on how well they meet the criteria of your personal value equation and how they compare when you are making final choices between them.
You can read more of my thoughts about the differences between a latex/polyfoam hybrid (and the Aloe Alexis which has two layers of latex vs one) in post #2 here and the post it links to.
Assuming it is actually the latex (which is less likely than the comfort layers of the mattress underneath it) then this would be uncommon but certainly not unheard of either and based on my experience and feedback from manufacturers over the past few years it would be more common with Talalay latex that is made by Latex International than with other latex manufacturers.
Phoenix