A lot of your "gaming" motherboards come with dual bios. In such cases, if you toast one you flip a switch and use the other. In most cases with motherboard with 2 bios chips you can boot from the good bios, download the latest version of your bios from your motherboard manufacturer, flip the selector switch back to the bad bios while still booted, and reflash over the bad bios it from within your OS. You would most likely lose any custom efi vars but your could easily reconfigure them as needed.
If your motherboard doesn't have dual bios or bios recovery system built in, all is not lost but you probably going to have to reflash the bios via an external programmer, but such tools are dirt cheap these days. heck you could do it from a Raspberry Pi and a SOP8 test clip if you don't have any other computer to reflash the chip.
If you want to be super safe, you could dump the contents of the bios flash chip using an external programmer before attempting to do any of this (Same tools as you would need to flash the chip, Another computer, and if that other computer isn't a SBC with SPI GPIO a cheap USB SPI tool - You could use a RPI Pico for this for just a few bucks).
(Dumping the contents of the chip via the bios provider / motherboard manufactures own bios flasher tool will often skip over parts of the chip. Looking at you Intel ME! - but if your only touching efi vars, a backup from the bios flashing tool should be good enough, just make sure you don't overwrite the areas the tool didn't back up, which is why I suggested using an external tool to dump the contents, much safer.)
EDIT: As for the risk? Well again it depends, you gotta be pretty unlucky to kill the bios because of a power failure right as your messing about with it, but it can happen. I went though a spell of "tinkering in the bios" for a while *cough*Windows SLIC*cough*, and only messed up the bios once during those years and I did a far bit of flashing back then, but I was able recover the bios using an external programmer.