I know how to turn a 3x3 into whatever sized grid I'd need, but thank you.

Let me try to clear my question up.

There are TWO grids that serve the same purpose of creating the lag effect (slowing down units in the affected area), but only one of them will be used.

Size is just an example.
Which grid would be better?
Grid #1: The classic 3x3 scourge/observer grid. Where the units are ALWAYS created and removed.
or
Grid #2: The 3x3 scourge/observer grid that creates burrowed units below to make a 3x3 ground grid. To produce the "lag effect" the burrowed units below will be given to P11, one unit at a time. Once P11 has exactly 9 burrowed units in the grid-area, those 9 units will be given back to the current player. Since lurkers are changing ownership, that allows a location to follow EVERY lurker. That specific location moves the lurker back to the exact same spot it was at, which creates the actual "lag effect".

I want to use the least map-limit-intensive grid. EG, which one will produce the least amount of sprites(if any), units, etc at any given time.

creating/removing constantly causes lag. I would move the units to its location to slow them down.

I may have misunderstood the problem your having but, just use devourers instead of scourges and observers lol... Saves trouble and they're perfectly sized to accommodate up to a 5x5 grid.
Using Cordinates: say I want to spawn my drone at (4,4) in reference to the devourers possible positions
DDDDD
DDDDD
DDDDD
DDDRD
DDDDD

Create 2 Devourer for [Computer Player] at Location A
Create 1 Devourer for Current Player at Location A
Center Location B on Devourer owned by Current Player at Location A
Remove all Devourer for Current Player
Remove all Devourer for [Computer Player]
Create Drone at Location B
Preserve

Assuming you have Hyper Triggers ^ this works everytime perfectly and fluently with minimal unit lag even over multiple consecutive uses.

That's the opposite of what he's trying to do, though; he wants the lag effect. It sounds like it's going to be a spell or something along those lines, where he wants all units in a certain area to move slower.

Creating/Removing a mobile grid would use the least amount of resources (one location, only as many units as you need to cover the area, and those units are removed before the end of the trigger cycle). The act of creating or moving a unit is what causes the unit lag for any units under that unit (something about collision checks, I think), so removing and killing the units will not change the lag effect's effectiveness.

creating units means writing more data, which is why I think it's more laggy. I don't think it matters much in the long run though.