Don't think so. But I think your character level has lower impact than raising the corresponding weapon skill level (and other skills levels).
At least the stats you raise during the level up should make a difference.

The reason behind me asking is that the yellow lizards appeared only after leveling where before it was only red lizards.

From what I remember game doesn't add monsters if you clear the area. Maybe they just wandered in from the unvisited parts - unless you explored the entire area?

maybe mine has a glitch because when you rest the monsters that appear while your resting tend to get more powerful rather than less or equal to.