Shd0w2

If you're fine with being out a GPU for a while then go for it.

Give some prices in comparison to the cost of Ryzen for you.

depends if it is a good deal

Grab the 75Hz, Curved is neat but not really lifechanging.

450-500 USD is pretty low for what you want. Move it up to ~500-700 and it would be a lot easier to make a build for 1080p high-ultra gaming. Do you need a monitor and other peripherals like a keyboard and mouse?

Older as in used? or Older as in it was released a longer time ago? If you mean released a longer time ago, grab a Platinum PSU because even if it was released a while ago, it still conforms to the Platinum efficiency spec.

Looks fine, but if you want to put it in an XBOX 360 case, you may want to look into a smaller form factor PSU, like an SFX form factor.

Using a high end graphics card on technology that doesn't push it to its limits (Not 1440p 144HZ or 4K 60hz) graphics cards tend to run at less than their best because they simply don't need to. I'm not sure why your GPU usage is around 99%, however. Try getting your hands on either a 4K monitor or 1440p 144hz and see if the story changes. (As in getting ~60fps in 4K 60hz or around 120-144 in 1440p)

Your RAM has a lower CAS latency so it would be the one being downgraded. Lower = Better for latencies. It wouldn't be a huge deal though if you still wanted the RAM.

Oops, I thought I had put latency because I the speeds are both 3000mhz but the CAS Latency is 15 vs 14 / the timings

Probably would work, however, each SKU of RAM runs at different speeds and one would likely configure automatically to be the same speed as the other, meaning it would be slower.

If you don't care about their rigging of Phone Benchmarks, then grab one if you want. Android is fine and most devices work well, if you think you like the One Plus 5 then go for it.

Your settings for the benchmark may be different, you may accidentally have a taxing setting on for the benchmark.

A. Did you use different thermal paste? B. Did you make sure the new cooler was fastened properly C. The other cooler could have been somewhat faulty / lower pump speeds.

Try Downclocking the RX 460 to see if it persists. Also try plugging your HDMI / Displayport cable into your motherboard / integrated graphics to see if the issue persists.