Turns out, when combat happens in the same plane that exploration exists, enemies too must exist (unless everything is done in random encounters).
That may sound obvious, and it's kind of is, but there's some more details to the way we plan to approach this in level design.
Sometimes part of the fun in tactics RPGs is mowing down groups of enemies with the strength of playable characters. We wanted to keep this part of the fun, so having enemies outnumber the party is likely a common situation. It keeps a challenge as well as gets players strategically thinking how to beat the odds.
So then, how are we placing enemies?
There were a few approaches we considered. One of them was a reinforcements style, where one enemy on the map can be multiple enemies in combat. We weren't quite happy with how that felt when players make a strategic engage just to find themselves surrounded or overwhelmed by unknown enemy numbers. Instead, we decided to incorporate a grouping of enemies into the bounding box of combat.
Essentially, when the bounding box grows, enemies caught in it are brought into combat. Unless any enemy is specifically designed to summon reinforcements, no more enemies enter the fight than the number seen in exploration. This retains some more parody between the two game modes within the same space.
By grouping enemies into relevant camps, this also keeps the screen clutter low. When we were playing with the box and splashed enemies all over the level, it felt a little messy and overwhelming -- especially when every enemy has a patrol routine! This way, enemies can be mentally associated together as one relevant fight and also allows us to be extra creative with how enemies inhibit the worlds. And one more bonus, not every enemy needs to move and patrol anymore.