It’s been a while since I tried Haiku. Beta 5 is the best experience so far for me. I’ve been looking at Haiku sporadically for 10-12 years, and beta 4 is the sharpest experience.
I had to manually build the UEFI loader setup, which has good instructions and works a treat. The only thing I’d suggest in the help file for UEFI is that it should be made more clear that haiku_loader.efi needs to be renamed to BOOTX64.EFI. Keep going, I think you’re almost there!
It depends onthe computer firmware, as far as i know.
Haiku doesnt yet have the infrastructure to srt up NVRAM entries for the boot menu, but that would allow booting arbitary efi filename (FIXME).
Yeah, I went round and round a couple times before I realized the default install was using legacy BIOS. I guess it helps to RTFM. My computer has only UEFI, no BIOS. So, once I read the UEFI instructions on Haiku-os.org, all was well 
I agree. EFI seems like the least understood computer interface ever. It originated in Itanium.