Dave, I responded to a similar thread elsewhere.
In regards to how many DSV2 units in each building, first, it depends if you are counting the number of keys/locks. That is, all units are lock offs. I would guess that on each floor there are probably six (?) 2 BR units per floor per building. So, that would be twelve 2 BR units per building or 24 units (both efficiencies and 1 BR) per building. I could be off and perhaps it is eight 2 BR units per floor per building or perhaps four.
Patio size versus lanai size? They are the same. But if you're on the first floor, you could place the chairs on the lawn and effectively expand that area beyond the concrete.
If you booked a 2 BR unit, you will have 2 patio areas. If you booked a 1 BR, you still have a decent sized master patio that could accommodate 4 people. If you booked an efficiency, then you may be a little "tight" on patio space for four people. But if on the first floor, you could place chairs on the grass. I kind of recall that the efficiencies only have 2 chairs.