I tried all three, multiple times, and it depends.

Using the last workload tested as an example, mimalloc just consumed memory like crazy. It was probably leaking, as it was the stock version that comes in Debian, so probably quite old.

Tcmalloc and jemalloc were neck to neck when comparing app metrics (request duration etc... was quite similar), but jemalloc consistently used only about half of RAM as opposed to tcmalloc).

Both custom allocators used way less RAM than the stock allocator though. Something like 10x (!) less. In the end the workload with jemalloc hovers somewhere around 4% of the memory limit. Not bad for one single package and an additional compile option to enable it.