If the landscape lamps are the round flat type with 12 or 24 surface mount less, they should work quite well. The 12 led are type 5050 and the 24 led type are (if I remember correctly) type 1210. If they are in warm white, and if you are happy with the light output, try them. They are cheap enough.
I have used the 36 type 1210 and the 15 type 5050 led panels, and I prefer the 15 type 5050 ones. On the 36 led panels I notice some shadowing when I read, and the denser layout seems to result in soldering problems that cause one or two groups of three to not light.
I've not noticed any rfi problems, but wouldn't expect to with fm or digital TV. I mostly camp off grid and value the reduced current draw. Plugged in at home they work fine.