To be clear, I'm only suggesting that Mango router if (a) OP is nervous about installing OpenWRT without a backup device and (b) he can't find some secondhand compatible device even cheaper.
Don't get me wrong, I also have a Mango router that I bought on a whim years ago on sale for maybe $10, and it's fine for what it is, but paying $30 for it today should only be a last resort. OP doesn't need anything beyond the (presumably compatible) TP-Link device he already has.