Haiku wants to reboot after every install

If rEFInd does not find Haiku, you probably just forgot to copy the EFI bootloader to the EFI partition like you had in your previous install. That is not yet done automatically on installation.

Having created the partition yourself, you have to set it to the corect partition type. For a GPT disk that is 42465331-3ba3-10f1-802a-4861696b7521. Notice this is the type of the partition, something different from the type of filesystem you format it with. See, for example: Adventures installing Haiku to MacBook Pro (11.3, late 2014, on SSD, EFI) - #3 by Zenja

Wrt the snapshots, that’s a feature in Haiku. Whenever you install or uninstall a package, that state is backedup so you can go back if anything is wrong. It’s not a full snapshot, though, just the installed packages.