Since the question about "what LEDs should I use" tends to come up frequently on the forums, I thought I might write down when I generally like to do for most games.
I've been using comet pinball bulbs for years--they've always worked well for me. There are of course, other brands available, and each one has its fans, but I've been happy with comet's products & prices, so I've continued to use them. So with that in mind, those will be the bulbs I'll mainly be referring to, though I think most of the common bulb styles I'll be referring to are also available from most of the major bulb manufacturers.
When it comes to white LEDs, there are generally 3 color temperatures available--warm, sunlight, and natural/cool. With warm bulbs, the color looks a bit yellow. Sunlight is roughly neutral, and natural/cool is a bit blue. For most things, I generally go with sunlight.
Typically, for GI on solid state games, I use: 1smd sunlight frosted. Sometimes 2smd in darker areas.
For the backbox, I typically use natural/cool 1smd bulbs. Depending on the look of the backglass, sometimes I use frosted, sometimes I use no lens. Although, more often than not, I use frosted with translites, and no lens with real backglasses. I never use clear lens since those typically cast rings on the translite/backglass.
For inserts, I typically color match the red, blue, green, and purple inserts. I use sunlight bulbs for orange and white inserts. No lens on bulbs pointing directly at the insert, and for bulbs that are sideways, I either use flex head or frosted. For small inserts, I usually use 1smd. For larger inserts, I usually use 4smd or 2smd.
The only time I use warm LEDs is on EM games. The GI on EM games is also the only place where I might use clear lens blubs to try to replicate the look of incandescent bulbs, but only if the bulb is visible to the player. Otherwise, I stick to either frosted lens for bulbs hidden under plastics, or no lens bulbs for inserts. With the clear lens, the bulbs tend to cast visible rings of lights on backglasses, inserts, and plastics.
The only time I use cool/natural is in the backbox, especially with yellowed translites, to help offset the yellowing.
I never color match plastics on the playfield or colors on the backglass. I think doing that just overpowers the existing colors of the game. But, some people like to do that; however, it's just not my personal preference.
For flashers, I generally use the 5smd, 8smd flat, 8smd tower, and 8smd flex head. If a flasher is basically directly visible by a player, I'll use 5smd. If not, I'll generally use an 8smd flat or tower. Flat; I'll generally use if the bulb is basically being directed in a particular direction. Tower; if if the light is omni directional, like under a large colored dome. Flex; usually if the bulb is sideways, especially when there's a large insert in the center of pop bumpers. I generally don't color match flashers, and pretty much let the domes/plastics/inserts do the work. In special cases, I've used 10smd flashers, such as in the AFM mothership saucer.
That is generally my approach to adding LEDs to games.
As for non-ghosting bulbs, I haven't needed to use them. Most games don't actually need them, since there are often workarounds for ghosting. Plus, it's less expensive to just stock one bulb type, and non-ghosting bulbs are generally more expensive than their standard counterparts. For classic bally/stern, the siegecraft LED add-on boards work fine. For WPC, just use the LED ROM patch fix. For Gottlieb System 3, the ghosting is so minor, it's barely noticeable. I can't really comment on Stern SAM/Whitestar since I haven't worked on those extensively, but in some of those games, it sounds like they may need non-ghosting LEDs (if you aren't using LED OCD boards).
If you can install LED OCD boards, I'd highly recommend it. In most games, LEDs don't fade in and out very well. Sometimes they will just cut in and out, sometimes they will flicker. With the LED OCD board, it reproduces the dimming features for lamps very well, and greatly improves the game's look and light shows. For games that have dimming features in the GI, I'd also recommend the GI OCD board. I just wish these boards would be available for pin2000 games--proper dimming effects with LEDs on those games would look terrific!