I have a very small house and have begun wiring rooms with 12/2 with 20
amp breakers. I realize this is overkill especially for overhead
lighting (of which I have only 2 lights). But the increased cost
doesn't bother me and it makes my circuits and wiring job much simpler.

Also most of the lights and switches are rated for 15 amps with the
exception of outlets which actually need to support appliances
requiring a 20 amp circuit. The overhead lighting shares the circuits
with other lights and outlets.

Are there any problems wiring this way with regard to safety or code
violations?