You can’t power two 5K displays with any M1 mac.
I don’t know if the 5K LG has the YPbPr problem. There’s no way to verify it on these monitors. We know for Dell because the OSD mentions it. EIZO also confirmed the issue and published a release note and contacted Apple About the problem.
If sharpness is your primary focus, 4K 27 inch > 4K 32 inch.
If real estate is your primary focus : 4K 32 inch > 4K 27 inch.
Why ? Pixel density is obviously higher on 27 inch, but you‘ll need to scale the text for confortable reading.
I think both U3219Q or LG 32UL950 are your best choice if you want 32 inch. The LG seems to have a superior HDR performance. One in USB-C, the other in HDMI. Have certified HDMI 2.0 cables please (like
https://www.audioquest.com/cables/digital-cables/hdmi-4k-8k/pearl). this will avoid you a lot of problems.