Foam: The most effective, by far. I suspect many people wear them incorrectly and do not insert them far enough. You can use lube (they make special ear lube for stuff like hearing aids, although I think anything medical grade will do) if you have difficulty doing so. I have unusually small ear canals; the most comfortable and best I've found by a mile are Mack's Ultra Soft Foam Earplugs. These are much more comfortable than slim fit alternatives and also have very high attenuation.

Silicone: expensive (but they're reusable and last years), but the least fussy once you get them. They are moulded to your goddamn ear---it's a perfect, pressure-free fit every time and they go right in. Drawbacks include lesser attenuation and attenuation that isn't immediately at 100%---it takes a while for it to "seal". I abadoned these once moisture started to accumulate between my ear canal and the plug and I'd hear it as I moved and it became very annoying.

Wax: joke attenuations compared to foam, and bad compared to silicone. The most expensive long-term unless you're serious about reuse. Somewhat fussy and may fall out. Very comfortable (little insertion).

Foam + wax: this is what you really want if you care about maximum attenuation. My ear canals are slightly too short to comfortably insert an entire Mack's earplug, so I snip the ends off mine, lube them up, and insert them completely flush into my ear canal. Then, I take a wax plug and mould it on top. It's perfectly comfortable and it performs better than any other option I'm aware of. I tend to also wear a Bluetooth sleep mask and play rain sounds on 100% volume and it just comes through the double earplug situation to mask any very loud/spurious noise. To remove the flush-inserted earplugs, I use a pair of blunt tweezers.

When I used slim fit foam earplugs I'd routinely get ear infections. Switching to silicone fixed that, but suffered from the aforementioned issues. With the ultra soft earplugs + wax method I never get ear infections. I make sure to always insert a fresh pair (but I reuse the wax ones for a few days) and to always do so with clean hands. I think the infections are due to friction between the plug and the canal during insertion as well as plugs that are too large/exert too much pressure once expanded---the lube and very soft plug addresses those issues.

[1] https://paxauris.com/