Yes it does make a big difference when each light only draws a small fraction of an amp. The interior lights are all from eBay. I searched on "12v LED, warm white, MR11" where the bulb base type was MR11 for my existing interior fixtures. (You might have bayonet or other.) The bulbs were typically $5-10 each. I needed about 17 of them so I bought a few singles to try out before committing $ to the whole lot. This worked out well. Usual eBay caveat: check seller reputation and note that most of the cheapest prices ship direct from China, so if you want fast turn-around order from a US seller.

For nav lights, I used CG approved LEDs and spent quite a bit more. I also hang some Bebi OWL lights near deck level when anchored, and would recommend them but unfortunately they're out of business.