I wonder what this will look like when integrating with other apps. I don’t think there’s a standard ical type for birthdays, for instance.
I can’t really say I can find a use for this feature (all the birthdays I need to remember are in my contacts too) but I guess it’s useful if you just want to jot down someone’s birthday but not their name or phone number?
Bleeding edge or easy to use, take your pick. I think Suse and Endeavour are your best bets for both but neither do both perfectly.
As for Wayland, assume it doesn’t work but maybe you’ll get lucky. As for lightness, I find Gnome and KDE to work perfectly fine even under performance constrained environments. Depends on what you call “light”, I guess. The biggest differentiator these days is (the lack of) hardware video acceleration, on all platforms.