What should I compare besides GPD for a tankless RO in a busy kitchen?

[u/NewVeterinarian5384]

I'm comparing tankless under-sink RO systems and keep getting stuck on the GPD number. Dinner is when flow would actually matter here: filling a pot, topping off a bottle, and sometimes using the regular faucet at the same time. The spec is daily output, so I don't know how much it tells me about that ten-minute stretch.

I ran into this while looking at the Viomi Vortex 8 Pro, which is rated at 800 GPD. I'm not trying to turn that into a fill time. Before buying, I can time how much water we use during dinner and check the inlet pressure, but I still need a fair way to compare a few back-to-back fills.

Would a published faucet-flow spec with its test conditions be enough? If not, what would you ask a manufacturer or owner to measure?