Got RO Unit finally!

[sphelps]

50gpd = 50 gallons in 24 hours, but that's ideal, most of the time it's lower.

You can run it for a bit but 20-50 gallons of waste seems a bit much, as soon as you get a TDS reading you're happy with you're good to go.

You can add DI anytime

Yes safe to drink, both RO and DI, DI will may taste funny but it's not harmful. I drink RO/DI water.

Get an inline TDS meter, it will tell you when to change pre-filters. An auto flush is also nice or remember to flush the membrane often.