You can convert a MBR drive to gpt. But if a second drive I suggest an efi partition as the first partition even if grub will install into the first...
The default is the Unity with the icons on the left side. My monitor is 4:3 so I have more space on top & bottom so the old layout works better, plus...
I do not use nor know about encryption. But un-encrypting your partition(s) is what Boot-Repair needs to be able to repair it. It also has a link on...