My recommendations probably change subtly over time because I'm always still learning what people are using and how well it works for them.

For backboxes, I'd recommend 1SMD frosted bulbs.

You do not need non-ghosting, those are only ever needed for inserts (and even then, not always).

If you choose a clear lens, it's very easy to get a spotting or halo effect, which might be fine for certain places, but using them throughout the backbox will almost certainly leave your translite looking like a leopard! This is why I recommend frosted.

You also can't go wrong with using mostly white. Warm white (which is closest to the color of incandescents) for warmer artwork, natural white for colder artwork, and sunlight for something in between. Using colors in the backbox will look good too, but I recommend using them sparingly to highlight a very distinct color, hopefully in a way that the color won't bleed into the surrounding artwork.