the 'by far the best' manufacturer of mutable instruments is - mutable - ergonomically sound and great support, plus the original designer gets the money not some guy(s) who took a github plan for a module and shrunk it - mi also have great support!
black panels can be had for most of the mutable modules from various DIY stores
in the long run the cost savings are minimal for most modules and the space saved will be irrelevant once the case is full and you need to buy another anyway
I own Tides (both), Plaits, Marbles, Veils, Branches, Links, Kinks, Peaks, Streams from the factory and a couple each of veils, shelves, ripples and shades that I built and a few in the DIY backlog
I don't really have a favourite/least favourite - they all do what they are supposed to very well
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities