Timeshift to external drive specifics

I plan to delete my Windows 7 dual boot but wanted to back up to an external drive. I currently have Timeshift snapshots on the internal disk.
After searching around, I’m a little confused as to what type of file system is best for snapshots. The BTRFS is stated to be for snapshots per the Disks dialog. Other info I have read is that BTRFS isn’t necessary.
Any concrete clarification?

I do not know. @vasileios may be able to help.