At 8x8, you really only need around 2000 x 2000 pixels (4MP). That's based on a common photo lab standard of 240-250 PPI.

My 16MP GH4 makes an un-cropped square image 3456 x 3456 pixels. This makes a phenomenal 14" square print without interpolation. Resized with interpolation to 7500 x 7500 pixels, it makes a very respectable 30x30, too, since the viewing distance is 1 to 1.5 times the diagonal, and for either size, there is the SAME relative resolution when you view at the same relative distance (1 to 1.5 times the diagonal dimension of the print). Now, if you pixel peep, you'll see differences between 16MP and 24MP at that size. But at normal print viewing distances, the difference is slight.

I have an 8x8 on my shelf above my computer of a sunset on the lake down the street from my house. I took it with my old iPhone 6s Plus. It looks more than fine...

I had to do all the math back when I ran the printing departments of a pro digital lab, about a decade ago. We were making HUGE prints from 5.3 MP Nikon D1x images. As long as you enlarge the image with decent interpolation software (or methodology), the images look nice. I'd rather have been making 40x60s from 24MP or 36MP or 50+MP files, but it was 2003...

I laugh when I see some of the hair splitting that goes on here. Almost everything on the market is damned good, now.

This is a very timely topic. I have a Nikon D810 and a bag full of pro glass. Generally enlarge up to 20x30 with some 16x20 work as well. Most excursions are for shooting. Occasionally my wife and I do some casual photography like on our cruise in mid-January. She thought I should take fewer lenses than i did and we have a "discussion" while packing. She is using a Olympus E-M5mk2 and has lenses from 7mm to 300mm, but they are 4/3 size.

My long-suffering wife suggested that I investigate buying a Olympus 4/3 body and share her glass for less serious outings. Yesterday, we went to one of the local shops. I did not like the feel of the E-M5mk2. Too small. The new E-M1mk2 felt really good but I could not wrap my head around the CAD$2500 price tag. The salesman then suggested the E-M1 orig. Wow, great in my hand, almost the same features and menu (and same battery) as the E-M5mk2 and the last one in Toronto was priced at CAD$995. Bought it on the spot. Set it up last night and love it already. It will not replace my D810, but it will be better when taking a stroll with a camera. Thanks Olympus for saving my marriage!