Netgear R6350 - Recover to stock

Hey. I'm a user of the Netgear R6350 and recently have had issues with OpenWrt. I would like to recover to the stock firmware. I have the link and all, but I've found that there's two recovery methods - nmrpflash and sysupgrade (via luci or cli). Sysupgrade seems safer, but I'm not sure. Is stock even sysupgrade compatible? Please, point me in the right direction so my router can be normal again. Thanks in advance!