Cinema means you want 30-40 degrees, but once you've fixed your screen size and your distance, you can then work out if 4k is worthwhile over 2k (or 8k over 4k)
Of course this all falls down because it them comes down to availability, other features (number of hdmi ports, "smart" options, power use), and "4k" tends to also mean things like HDR, which is worthwhile (with the right source) no matter the screen.
