As a general guide: Quad HD or 1440p (2560×1440) is the same real estate as 720p, but at 2×; 4K (3840×2160) is like 1080p at 2×; 5K (5120×2880) is like 1440p at 2×; UHD is not consistent at all — divide the device’s resolution by two to get the real estate.
1080p actually needs 4K equulvant pixels for macOS, unless you want the blurry version