I'm fed up with my 24-105mm f4 behemoth and was wondering if I upgraded to a 61mp camera, could I use primes instead and then crop in? If I crop 2x I'd be left with 16mp, which should be enough for a medium sized print, or filling a 32 inch 4K monitor.

Will my images look less sharp and more noisy (shooting at 100 ISO with a tripod) doing this vs zooming in and then downsizing the image in post to match resolution?

I'm thinking I could carry:
> Zeiss Loxia 21mm f2.8 (cropping up to 50mm)
> CV 50mm f2 Apo-Lanthar (cropping up to 100-125mm)
> Sigma 90mm f2.8 (cropping up about 200mm)