Would love to try the Outemu Peach and Lime switches. I use both U4 and Midnight Pro (the very lightly tactile one) and I enjoy them both despite the latter being more noisy, it makes a very soothing marbly sound on in my kbd67 lite (PC plate, foams).

U4 was the quietest switch I had tried until Mode Anthracite. They initially felt too heavy, but they're growing on me. I'm so pleased that mode even bothered making a silent switch and they bring something new. Less tactile than U4 but still noticeable.

To make a quiet keyboard you have to start with the switches, they are the source of vibrations to begin with. But the plate material and case have a lot to say what happens to the sound that is left. A metal plate in an open case is certainly going to accentuate any spring ping, leaf making contacts and plastic scratching.