I voted for 4K monitor even though I only have a 2K monitor (27 in) myself, but I like to zoom in to see details. I usually don't print, but perhaps I'll change that in the future. I had a few images printed in A4 (210 mm * 297 mm / ~ 8 in * 11.5 in) on paper before, but have just this week seen an offer for a picture in 80 cm * 60 cm (~ 31.5 in * 23.5 in) behind 3 mm acrylic for 20.80€. I added their mounting bracket for 10€ and now
this squirrel (cropped down to 4:3 ratio) is hanging on my wall. Looks nice in larger than life size, holds up to viewing much closer than the diagonal, and it was dirt cheap. I think I could even save the mounting bracket and use adhesive strips for safely holding that size and weight on the wall. Will keep an eye open for special offers on smaller sizes in the future.