A typical subdivision approach would avoid using meshes of different densities where possible, and rely on Catmull-Clark subdivision to create curvatures/circles..
Any (6+)-gon will make a reasonable circle under subdiv. Often made from 4 quads:
- Select all quads
- CtrlX Dissolve central vertex
- AltP Poke single face
-CtrlShiftB Bevel central vertex
- Shipped Add-On, Loop Tools > Circle the result
Then, with extrusions, and some rotations/scales around Custom Orientations, you can model something like this mask without having to reduce topology to match between densities.
If you do really need to match areas of significantly different detail, often, to avoid fiddly hand work, you can model at a lower level of subdivision than your intended result, apply one level of subdiv, and continue modeling from there.