Will this 199k tankless keep up

CBRob

@Zman

Got a couple of new homes that I'll be managing as rentals soon

They are ski area rentals, 4 bedroom 4 bath
The whole home is heated and  DHW with one nevian 240e
That's 199k btu dhw before adjustments for altitude.
Ground water probably around 40f and 70degree delta 4.4gpm before altitude.

Should I expect  to see some shortcomings from this system when this house gets rented? 
This is the first time I've seen any home here using tankless dhw.
The 240e combi unit looks so small, and has 2 inch vents.

9700 ft elevation.

Zman

At 2% per 1,000 (swag which is usually correct for appliances with burner),
I am coming up with 5.12 GPM with delta 70 and 90% efficient and then 4.14 GPM after altitude derate.
I guess it depends on how many tubs and big loads they have. Some combi's will restrict flow in order to avoid cold water going to faucets. That way you get complaints about low flow rather than low temps.
I don't have any experience with Navien. You might just try running everything at once and seeing what happens.