I'd argue that there's almost certainly another solution than covering the entire map in regions.
1) I've heard that too many Regions can cause problems, but it was mainly associated with the Event "A unit enters/leaves region". If you can keep that Event usage to a minimum you could potentially avoid this issue.
[Crash] - Using "Unit enters in (Playable map area)" event breaks my map
2) Look at #1.
What are you trying to do that requires so many regions? Could you instead use Points and X/Y coordinates?
It would exactly be for unit Enters/Leaves a region types trigger. Actually, it would be for just Enters regions, as of now I have a system that detects what part of the map a unit is with both Enters and Leaves in use, but there are still decently portions of the map not covered by any region.
I want to add a teleport-style ability to my map that allows a unit to change where it is, but if it teleports to another unit that is in-between regions it may cause minor errors.
My goal is to cover the entire area that's path-able to exclusively Enter regions and have none of these regions overlap, thus I know exactly where a unit is at all times without having to add leave triggers (The Enters can just handle most of the leave logic).
Two example of the current region system. (Just the blue ones, i.e. the zone wide ones, are of interest here)
Whenever a unit enters the blue one it lets the game know they have entered a new region, these means there's a little bit of a blue in between one region ends and another begins (since I'm only using Enter events), but it works pretty well for ground pathing units, or flying units that's are bounded by blockers.
Right now this ~75% coverage manages to capture >99% of movement between regions because of pathing restrictions. I.E. characters have to one from one zone to another and one can know where they are simply by the last one they entered. I'm expecting this to be occasionally thrown of when a character teleports to allied units in between the blue, and I don't want to have to add a "leaves" trigger to each blue zone, instead, I was thinking of making the blue accurately cover each zone thus accurately tracking where exactly a character is at all times.
As of now the game runs pretty smoothly.
EDIT: For context I would use just leave and enter triggers with the current system, BUT I've noticed it's not always consistent as to which of these will run. I.e say one unit leaves on region and enters another, I need to make sure that either the leave or enter will always execute first. As far as I have tested leaves and enters don't always execute in the same order. Sometimes the game triggers the leave first and sometimes it takes the enter first.