click start > type system information > check BIOS mode is UEFI or not
if yes you are good to go
if not download rufus (google it), set like the attachment photo, and install when your ssd arrive
as for your lag probably you need to explain more, I am using same laptop with you, have been used it almost 1 month no lag at all
*have been used it without ssd for 1 week, then install ssd