Yes, one day park hoppers are available and the UG even has a great plan for splitting the day. It is quite the expense to get the park hopper for just the day and I don’t think I’ve ever seen a discounted 1 day ticket for DL ever, but I still could not imagine literally being steps away from one or the other and not being able to go in. I would only ever suggest it if you were a strong fan of one park over the other. EDIT: To clarify, I would only suggest sticking to one park (vs. getting the PH) if you happen to love one & only mildly care about the other.
Funny you should ask about MaxPass… I just gave a rundown in my last response to someone asking: Fast Pass option for tickets? - #2 by lolabear_la
Let me know if that answers your questions on it! We’ve only tried it out the one day & I loved the convenience but it is a lot of extra $$$ for me to add for the whole family to our Annual Passes so we haven’t made that jump yet.