I just picked Alpine Linux for majority of security and efficiency out of the box. It still required a lot of configuration, for lowering attack surface and hardening.

I know you asked for a lightweight distro, but from a security standpoint, I recommend using whatever allows you to relock the bootloader. Which looking up I dont see any choice. If relocking doesnt matter, then any distro for speed is basically any distro that comes with as minimal stuff as possible.

Also, I might be wrong so do some research