Here's the story for the TP-Link Archer C7 v2 (that's a device I'm familiar with). There are several rc2 images for Archer C7 at: http://downloads.lede-project.org/releases/17.01.0-rc2/targets/ar71xx/generic/
There are three "Factory" images: EU, US, and "no-country". Use these to flash LEDE starting from the vendor/stock/factory firmware. They counteract the "region locking" that TP-Link incorporated.
lede-17.01.0-rc2-r3131-42f3c1f-ar71xx-generic-archer-c7-v2-squashfs-factory-eu.bin
lede-17.01.0-rc2-r3131-42f3c1f-ar71xx-generic-archer-c7-v2-squashfs-factory-us.bin
lede-17.01.0-rc2-r3131-42f3c1f-ar71xx-generic-archer-c7-v2-squashfs-factory.bin
There is a "sysupgrade" image, that will upgrade any LEDE image. (LEDE firmware removes/ignores the region locking):
lede-17.01.0-rc2-r3131-42f3c1f-ar71xx-generic-archer-c7-v2-squashfs-sysupgrade.bin
NB: There is also a TP-Link Archer C7 v2 IL router manufactured for Israel that is sufficiently different from other Archer C7's that it has its own build. These are:
lede-17.01.0-rc2-r3131-42f3c1f-ar71xx-generic-archer-c7-v2-il-squashfs-factory.bin
lede-17.01.0-rc2-r3131-42f3c1f-ar71xx-generic-archer-c7-v2-il-squashfs-sysupgrade.bin