You are comparing an older high-end GPU (GTX 980 ti) with a newer lower-end GPU (RX 560). Kind of like comparing an old muscle car with a modern economy car. Both are better than the other by different measures.
It is not, its just perferable budget card for games.
But against older gen high end cards it is.
Same as Nvidia does, if they cannot use the GPU core for high end cards they will try to make them as low end cards.
An RX560 and GTX980Ti are NOWHERE near the same performance category. You can't expect an RX560 to match GTX980Ti level of performance. It costs 1/3 as much.
Just found out that there are two version of the card you can buy. One is with 6 pin the other one is not. I got the bad one but after maxing out power consumption in wattman things are better. I guess with a freesync monitor this is a good card.
Edit: Forget about that. Even by switching to a gtx 970 (that you can buy for less money) you go from unstable 30 fps with minimum details @ 720p to stable 60 fps at max settings so what is going on. Card is a scam.