Different levels are optimized for specific mission types according to Sexy Exile Wiki guides :
For missions requiring you to "hit no mines," you can stay safely behind an obstacle and wait for the timer to run out to complete the goal. Combo & Score Management Sexy Exile
Combos have hidden decimal values (e.g., 4.1 to 4.9). To stay within a specific combo range (like "stay under combo 5"), aim for a sub-score of 4.5 to 4.8 by selectively avoiding some hearts. Different levels are optimized for specific mission types