Which settings cause high memory usage?

[GioF_71]

Hello, last saturday I had to drop three indexes from my minimserver configuration to lower memory usage to acceptable levels for my old RPI 3 (1GB of ram, to be shared with BubbleUpnpServer and a OpenVpn client connection to home vpn server for on-the-go availability).
I think the growth of memory usage has been determined by the growth of the library itself as it was long time ago I did the last changes to the indexing settings.

I also had to change a few settings on itemtags. All went ok, those action sorted the desired effect as now the server does not crash due to lack of memory. Awesome!!

Now my question: do "tagFormat" also contribute to higher memory usage? If I had to bet I'd expect the most relevant settings are in "indexTags" and "itemTags", followed by "tagValue".
Also my guess is that "itemSort" is used only when presenting the lists to the user.

Thank you for any help! Your answer will be useful in case I need to act again, so that I can drop the lowest amount of functionality in order to bring memory usage down.
For the near future I have a old Celeron J1900 mini-itx system with 8gigs handy but it will require full reconfiguration, so I'd like to stick with the Raspberry 3b for some more time.

Again, thank you.