Most modern CPUs have the capability to report their temperature --
shows up in bios stats.

Seems to me as measured by CPU self report, liquid cooling, which
costs over two hundred dollars, does not get you anything markedly
better than air cooling, which costs about forty dollars.

Has anyone obtained worthwhile benefits from liquid cooling?

Seems to me that ninety percent of cooling is getting good thermal
contact between the heat sink and the CPU, and the rest is merely a
detail.

Of course liquid cooling will give you some benefits on the disk
drives, but you have to space the disk drives, and if you spaced them,
you would get some decent air cooling without doing anything special.