You have many choices. Although not the most minimal, I think you will have the best trade off between minimal/unwanted stuff and ease of setup with Debian stable. During installation, selecting
Expert Install will give you the most choices - you can enable/disable certain services and opt out of installing a desktop environment. You will probably still want to disable a few more services after installation, but the base Debian install is fairly minimal. Additionally, Debian's stability may have a positive impact on your testing.
Most likely, you will have access to the same (or very similar) benchmarking and performance testing tools regardless of what distribution you choose.
I do not think you will see much difference in your performance testing between distros (solely due to the distribution). However, between different kernels might be a different story (would be interesting to see). Additionally, if a distro has a proprietary driver for your CPU, and another doesn't, the use that driver may change things. Debian's non-free repository usually has this stuff.
As for settings, if you do not disable swap, you'll probably want to reduce swappiness:
vm.swappiness=10 is often recommended for database applications. There are all sorts of kernel parameters you can tweak, changes to scheduling you can do, and so on. However, a few minor adjustments to virtual memory is probably going to be more align with the real world than super tweaking and optimizing.