An official 4K UHD release with open matte is not common. Most "4K open matte" versions available online are fan-created, often taking the 1080p open matte broadcast and upscaling it, or combining it with 4K HDR theatrical releases.
The 4K resolution, also known as Ultra HD, offers a significant upgrade in image quality compared to standard HD. With a resolution of 3840 x 2160 pixels, 4K provides a more detailed and nuanced picture, with a greater level of color accuracy and contrast. This is especially noticeable on larger screens or when using high-end display equipment. blade runner 2049 open matte 4k download link