Re: low voltage incandescent
If the bulb screws in, you can use it. There shouldn't be any problem using a product rated for a higher voltage on a lower voltage circuit. Go the other way (low voltage device on a high voltage circuit) and you could have problems. The voltage rating on things like lamp sockets and wire is for the insulation; insulation may fail if used with higher voltage than intended.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.