in short: 27" 2560x1440 or 34" 3440x1440, 120-165hz, IPS or VA
my experience has been that if you’re using a mouse, high refresh makes an incredible difference regardless of what you’re doing. if you’re using a controller or touchpad, it doesn’t matter so much.
it’s less about what you see, and more about how it feels. high refresh feels so responsive and smooth, whereas 60hz feels sluggish. this is true regardless of game. but the difference is much bigger with a mouse, because it’s such a fast way of interacting with stuff.
the biggest difference from refresh comes from the 60 to 100hz jump. the higher the better, but most would say diminishing returns starts hitting around 144-165. 240hz and 360hz are pretty niche products atm.
computer’s power supply has no relevance to your monitor.
4k is great on tvs, but it doesn’t make a very big difference at the monitor size. 1440p does look a lot better than 1080p though. 4k brings a lot of problems at the desktop. the performance requirement is extremely high, particularly for high refresh. you’re also basically forced to use windows scaling to comfortably use it unless you have eagle vision, which can be annoying and buggy sometimes. 1440p is a great middle ground atm.
panel type is important. the main relevant ones are IPS, VA and TN. TN isn’t great outside of a few niche cases, so let’s forget about that one.
IPS and VA panels both have great colours. IPS panels are more focused on accuracy, whereas VA panels can be a bit oversaturated to make the colours “pop” a bit more.
IPS panels have better viewing angles, with basically no colour shift at all while VA panels have some when not viewing from the front. VA panels have better contrast, so blacks are a lot darker. this makes a big difference if you play in the dark. IPS panels generally have lower response times, VA panels vary a lot in this regard from model to model.
viewing angles and contrast are true basically all the time between the two. colours vary from monitor to monitor, as does the response times, but they’re overall patterns.
my general recommendation out of the 2 for someone who strictly consumes content without creating is VA. the sometimes oversaturated colours can be very pretty and the higher contrast makes for a better experience in the dark. the higher response times are not that big of an issue, particularly if you get one of the faster ones. the viewing angles are not nearly as problematic as TN, and you generally sit pretty straight on from your monitor.