You sure can use the mats instead of sand. There was a thread a little while ago that did just that. They love it. You can also use the foam house panels. You will have to triple tape any of them to make sure they do not gap.
Now saying that you HAVE to have the area level no matter what you use under the pool. That is the key to a safe pool. It is also the hardest part to do. There are many videos and threads about how to get it done. The main point is to dig DOWN to level NOT add dirt/sand to level up.
Removing sod-not fun but does need to be done. Once it is gone I would use double strength Round Up. That is my go to plant killer. When I say double strength I mean I add more Round up per gallon than the bottle says. When I want it dead I want it dead NOW! LOL
IF you end up using sand make sure to put a good tarp or ground cover between the sand and ground to help keep the grass from growing into the pool bottom.
From what I have read when researching my build is the sand is still used under either the mats or the pink foam (what I used). You level and cut the ground. Some use screenings to smooth out the ground. Cutting soil 100% level over a large area with no peaks or valleys is next to impossible. It's like cutting wood for a table with a chainsaw. The screenings even out the surface and are compact able. Then the sand is like the drywall mud used before painting. When you use mats or foam you use just enough sand to put a fine finish to the bottom and achieve a level, even surface. In my case it was to cover the slats or strips which tie one side of the pool to the other. Would all this be required? It all depends on the size and type of pool and the ground condition and location being prepped. Help us with pool info in your sig.
i used the harbor freight mats under my pool and it turned out great. nice and soft. i think i bought like sixteen packages of them. that came to a total of 64. didnt use all of them. i think i had 1 package left. very easy to do. i just made sure all my pavers were level and then i left the dirt about half of an inch below the top of the pavers. after i had them down i just trimmed around them with a pair of scissors.
So, we used the foam boards and duct taped them together when we had our intex pool. Seemed great, nice feeling under our feet until we started feeling the seams under the lining and our liner started to bunch up a little.
When we begin our new Doughboy agp build, I know that we have to have sand brought in, but undecided if we will do the foam boards again.