Coolant overflow capacity?

I have been eyeing the recovery tanks that have the inlet on the bottom and a hole in the cap. I’m assuming that style would require the cap to be as high as the rad cap?

I check fluids before the first start of the day so it’s no biggie but in attempt to not spill coolant when I don’t have to…meh, maybe saint Petey will be impressed
I don't know. I'm not a fluid dynamics expert. How full is your radiator?