Yongnuo / Neewer flashes are very very competitive for off-camera work, as even the cheaper models contain optical or even wireless slave receivers etc.
Those cheaper models - like Yongnuo 560 models - are also "non-TTL", i.e. there is no metering electronics in them - you just set the % of power you want them to fire at, and those fire. That is easy to identify just by looking the hotshoe mount: there is only one contact for "fire". There is no other communication between it and the camera.
Think the x60
models are "dumb" and the x65
models are TTL - or something in this pattern.
So to be fair, for on camera usage those are not the same as Canon or Nikon Speedlights that do include TTL functionality in all their models.
Yongnuo's 565 series does tho, and those remain vastly cheaper, although according to some not as reliable @ TTL. Meh, that's good enough.
I think a YN560 IV set with or without the YN560-TX (guess you don't need it if one of the 560-IV is on-camera) is hard to beat for off-camera flash. I mean, Yongnuo was hard to beat having to buy the slave RF modules, bug having those built in? Insane, simply insane value for $.
I've noticed for some time now that Amazon has a 560 IV (before III) pair with a 560TX for around $220 shipped, which is silly as each 560 IV is $70ish and the TX $45ish.
i.e. $220 buy you 3x 560 IV or you can get the same set @ $190 as separate pieces with free shipping...what is the point of bundling?