I tried to verify those numbers by calculating the fee I paid for my coinjoin. In
this coinjoin, I used a segwit input and created two taproot outputs. With 6.03 sat/vb, I should have paid 6.03 * 69 + 2 * 6.03 * 43 = 934.65 sat, but I paid 1366.
Yep, assuming your calculations are correct, that means the decomposer forfeited 432 sats worth of dust that couldn't be split into equal sized outputs.
Where's this "Coinjoin to another wallet" option? I cannot find it in settings or in Wallet Settings.
It's under 'Coinjoin settings', which is within 'Wallet settings'. There's a bunch of nested menus that are annoying to navigate, but the devs have bigger tasks to work on than fixing navigation.