Very interesting! And riscv64 support! 
Are you sure about this? That definitely will affect the system in a meaningful way. Mounting the EFI partition at /boot means all your kernels and initramfs images will be stored on FAT32, so bye bye Btrfs snapshots.
I am not seeing anything in the docs you linked suggesting an EFI partition mounted at /boot/efi is problematic in any way, so I would say just leave it alone.
It is very easy to boot to Grub from rEFInd. In fact, rEFInd will detect existing Grub boot entries, automatically add them to the boot menu, and chainload Grub when you select one so you don’t even have to do anything.
You can also configure a stanza to boot to Grub from rEFInd like this: https://forum.garudalinux.org/t/how-i-installed-every-garuda-spin-on-one-partition/27353#configure-refind-7 Adding it into a stanza also allows setting up booting to Grub as a submenu entry, so it can be tucked away inside of your normal boot option if you want (as opposed to a separate boot option just for Grub).
…Huh. I mean, I suppose this boils down to a matter of preference, but…really?!
Look at this stuff!
There are tons of themes, it can look however you want! refind-theme · GitHub Topics · GitHub
I have to assume from this statement you are not writing your own rEFInd boot stanzas, and are just using the auto-generated ones for your boot routine. That’s no way to live!
If you write your own stanza, the submenus can be whatever you want. They can have alternate kernels or images, different boot parameters…you can even chainload other bootloaders like Grub. Here is an example of a custom submenu:
Writing a manual boot stanza is a little tricky if you have never done it before, but it’s not that bad once you get the hang of it. I wrote up a doc for the Garuda Wiki page that describes how to do it: Writing a rEFInd Boot Stanza | Garuda Linux wiki