Would this computer be strong enough for Unreal?

The first one, the FX 6300, is obsolete. You can work on it, but you will have a bad time. Old processor.

The second (Ryzen 2700 + RX 580) and third one (i7 8700 + GTX 1060) are great, and both have SSD + a good HDD (2tb on one computer and 1tb on the another one), and also 16GB of RAM. However, the Ryzen computer come with a RX 580 8GB Vram version, the i7 come with and GTX 1060, with 3gb Vram version. I would buy the second computer because of that, the amount of video card RAM on that RX 580 is more than on that GTX 1060.

If money isn’t a problem, you can consider to buy at least an RTX 2060 or an RTX 2070, because you will be able to work with Ray Tracing.

  1. If you don’t want to work with Ray Tracing, the Ryzen 2700 + RX 580 8gb version + 16gb RAM + 240gb SSD + 2TB HDD computer of your second post will be really great.

  2. If you** want** to work with Ray Tracing, an Ryzen 2700 (or i7 8700) + RTX 2060, or 2070 + 16gb RAM + 240gb SSD + 2TB HDD will be good.