systemd does not accurately report firmware speeds and can largely be ignored, as others have elaborated to. You can try reducing the skewed firmware speed by enabling fast boot / ultra boot, but I wouldn't advise that if you're dual-booting with another operating system, since sometimes it'll completely disable input and you'll need to go so far as a BIOS reset to fix it (I know from experience 😃). I believe the clr-boot-manager timeout also is calculated in, so if you have a timeout set and haven't need to boot into another kernel for a while, you could disable it entirely (we have Help Center documentation on timeout setting).
Realistically userspace is the primary thing that should be focused on, its one of the few things you have control of. The rest is going to largely depend on how fast the kernel can get loaded, initialize devices, load respective drivers, etc. as well as IO speeds. You might see a reduction if you opt for socket enabling for stuff like docker (if you happen to use it) v.s. the services, but once you reach graphical.target anything beyond it you can stop caring about IMO.
