By default Macrium can not override 32GB limit for flashdrives, horewer it is absolutely possible with third party utilities, like RUFUS It would be good to implement new features into Macrium, for example user can select UEFI only GPT mode for USB boot or MBR/uefi compatible, and NTFS/FAT32 selection. Currently I am using USB pendrive 128GB formatted to NTFS, GPT and it succefully boots in clean UEFI mode and in CSM nabled.