BTG Wallet DAT files

Hi all!
I recently downloaded and configured my BTG wallet. After almost 2 full days of downloading (???) I can now open it up and it appears to be working as expected.
One thing I don’t understand however, is the 155GBs of storage space taken up on
my hard drive by these “dat” files in the “blocks” folder!
Do I need to KEEP all these files, or can some of them be safely deleted?
On a side note, has anyone tried (recently) to mine BTG with an Nvidia GTX970?
I’ve got one that I’m currently using to mine RVN, but was just curious if maybe I should be using it to mine BTG instead.
Thanks in advance for any assistance!