How to "real" increase resources in NextcloudPI?

I have created a new VM and installed Debian 10, assigning 4 cores and 16 Gb RAM and a 200 Gb NVME disk and I notice that Nextcloud does not move as fast as it should, making a TOP of the machine resources I see that after being several days running it only has 1.3 Gb RAM in use, 1.8Gb in buffer/cache and almost 13 Gb unused, I’ve been trying to allocate more resources in “nc-limits” and when I try to apply more resources in nc-limits I see that the RAM usage goes back down to 750Mb of RAM, that’s why I wonder if the parameters I try to modify to improve the performance are really working, I’ve put 10Gb as maximum file size, 10 Gb for Memory limit, 12 php threads and 4 Gb for Redis memory
How can I check that these parameters are really being applied?
Any idea to make it move a little faster? I’m comparing with the other vm of nextcloud from hansson and I notice that this one is going slower, however I love the parameterization of being able to move the data of NextcloudPI