i doubt at this point a vega would be any better than a 1080ti, which is earning a lot now, i would not bother to much with vega for the time being, better to build a rig with nvidia and wait for the monster that will be Volta
The 1080ti is best for ZEC. But the ZEC is not so high price now.
1080ti is good for other algo like sia and skein which are very profitable currently, not only for zec or lbry, it a very good card because you can save wattage and a lot of space versus amd cheap gpu that need many rig to do the same