Calgarian,
As hnyman said, they are pretty much the same thing. When ssh'ing into it, the /etc/banner should spell out 18.06.2. Going forward, you can (1) flash viper-squashfs-factory from Linksys stock firmware's Web UI or (2) sysupgrade in OpenWRT with viper-squashfs-sysupgrade.
The older version of sysupgrade (LEDE 17.01.4?) can flash Linksys' stock firmware to another partition. I did it by booting from a USB drive.
EA4500 is one of most flash-friendly routers, with 2 boot partitions and USB booting capability: 2+multiple booting. Really hard to brick it and easy to test new code/settings.