Whole home 12-gauge wiring

I dont think I would. Just certain places like the kitchen (toasters) and bathroom (hair driers).

We dont have much of anything else inside the house that is a heavy consumer.

With little projects like this, you need to realize there is no ROI. No one is going to pay extra at re-sale. So you are doing it for yourself.

The problem is this is one very small detail, and you have 1,000 similar choices to make as a homeowner.

This may cost you only $1,000 more, but you have $1,000 to spend on 1,000 other upgrades also.

I noticed recently is that new 12 gauge and 14 gauge (armored or romex) was noticeably thinner than the older, even ones from about 10 years ago.

I recently did a lot of electrical work in my retail shop and a bath renovation at my mother's house.

I kept thinking I'd run the wrong wire when connecting the new ones and was also a little harder to cut them with the right gauge on the Klein tool.

Maybe they've improved the conductivity or just skimpy wire? Certainly much easier to work with the newer 12 gauge.

with LED lights being mandatory, you could, I guess theoretically, put well over a 100 bulbs on a 14 ga 15 amp circuit. (depending on Wattage used of course)

When I built my house, I used all 12 ga wiring. However, I did not hire an electrician and was doing this myself. So the primary reason was for bulk purchasing and commonality.

Definitely use 12 ga in all your receptacle circuits and anything with a potentially higher draw (HVLs, Fans, etc).

Lighting only really needs 14 ga, and it is much easier to work with. Terminating some of those 12 ga circuits with multiple branches can get tough. You can also start to approach box fill limits in certain scenarios.

It’s doable and not a major inconvenience one way or another, but it will cost extra for absolutely no real benefit.