Hi abbygrant,
Both memory foam and latex can be excellent at pressure point relief. There is also more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel” that may be useful as well.
As you’ve had a bit of a history with trying different mattresses and have a very specific sensitivity in your shoulder area when sleeping upon your side, it certainly might be worth a try for you, although I wouldn’t be able to predict if an all-latex product would work for you. The closest I think you tried before was the BME in a plush, which uses a polyfoam core. With your previous results, your key would be not having too much plush latex on top, but also not too firm of a transition layer. If you go this route, you may wish to try Talalay latex in your upper layers, as opposed to the Dunlop/Talalay combination you tried before.
Man of the site members listed in post #21 here are very experienced with assisting people with specific pressure point issues, and the help and guidance that they can provide on the phone can help you make good choices. There are a wide range of latex and memory foam and other options included in the choices there and I believe that all of them compete well with the best in the industry in terms of their quality, value, service, and transparency. One thing you may wish to specifically investigate would be a zoned mattress that allows for a bit more contouring for your shoulders, like this here.
I hope you’re able to find something that assists you in sleeping better. I know you’ve been looking for some time.
Phoenix