Every time someone asks for parts recc. and is very specific about what they want and how to perform is never a good time.
If you have the controller and switches/caps just build the thing, no one ever created a keyboard to fit everyone`s need, whatever you find to be "perfect" now, could become obsolete in 3 months or you get bored about RGBs and color shifting caps, breathing patterns...
You`re ready to dump $3k+ on "Best everything" ?
Best quality metal case ? Your local machinist
Best quality PCB ? Design one to fit your need
Best quality switches ? I dont even know what to mention here, so many sources.
Best quality caps ? Design, 3d SLA print, resin cast whatever you need or pay someone to do it.
Or
Use whats on the market and make the best of it which is the cheapest/flexible approach.
Just to make it clear, there is not alot of people that can afford to build hardware the right way, first time trying and keep it that way for years.
Been overly dramatic on purpose, once you start your own build you`ll understand why