If you try to fit Way with as many single cells as possible, you will get +4 more (248 total).
However this is not the best way of using space. Too bad there is no additional column in your tables that lists smallest buildings count. Maybe i will post some numbers later.

Way would be 492 rectangles (smallest park) + 25 triangles (smallest street).

Spire has a tiny bonus cliff, might be tiny, but it still has 4 sides to use ^^
Disaster to plan that tiny island though, but spire has water, pros and cons for the space you get as with every island. Like Way is the biggest one, but logistically a nightmare for your drones : )

Thanks so far, Guide is edited

Also, quite impressed at Spire's count, I hadn't realized the extra space is a lot of wall slots :o

North Coast - 36 Wall Slots
Quiet Coast - 31 Wall Slots
Heaven Water - 65 Wall Slots

Again, give or take 2-3.

Some more wall slot aproxximate counts:

Cascade - 37 wall slots. (only the top platform counts, pretty bad)
Spire - 76 wall slots. So far the best I've seen.
Heavenly - 41 wall slots.

Also your single cell count for Spire is off, you need to count the small cliff attached to it as well : )
My count of Spire is 189 single cells, not counting half cells(which would add another 12 or so)

Hey friendo! Some data for you.
Way - 73 wall slots. By far the best cliff imho.
Obsidian - 62 Wall slots.
Shard - 52 Wall slots.

These are quick count approximations, you can get more creative and maybe score 2-3 more slots. ;)

Yeah, I thought so, still a valiant effort, hope you update when you get to see them. ♥

@jdtuggey i made this at the start of the game and hadn't Wall buildings unlock ^^

Also important to mention that North Coast and Quiet Coast come as a pair, and are both missing a whole side of wall buildings, they make up in other ways but it's pretty significant, this is good guidelines, but not perfect :)