If you are talking specifically about a doorbell. Keep in mind they have wireless models available.

Would wireless models get interference from other electronics in the area?

"Would wireless models get interference from other electronics in the area?"

Considering the kind of luck you seem to be having with other aspects of your project, an interference issue is likely.

Just because a permit is not required doesn't mean the code is not applicable. An electrician that refuses to work according to the code just because nobody is watching should be sent packing.

Low voltage circuits are covered, but the rules are greatly relaxed for power limited low voltage circuits like doorbells and thermostat wiring.

The multiple amps of 12 V under cabinet lighting from a single large transformer do NOT meet the power limited requirements.

Higher power low voltage wiring that is concealed in walls must still use an approved wiring method.

Power limited - that is my new word of the day.

Are class 2 and power limited synonyms?

If you have a Class 2 transformer, then your wire still needs to be listed, right? There would be markings on the wire saying CL2? or CL3?

That wire, the CL2 wire, if it is so marked, would still need protection near studs?

Class 2 is one of the power limited categories.

Doorbells and thermostats usually fall into this class.