A few things of note. You don't need a 1200 Watt PSU, half that will be more than enough. There is little benefit from using a Core i7 rather than a Core i5 CPU for gaming as most games do not make good use of the ability to run more than 4 threads. The money you save with those 2 changes could be used to buy a much better graphics card, which will be far more useful for improving performance in games than a Core i7.
OnePlus 6T to be sold on contract in UK from O2, EE and Vodafone