I really don't want to use silver micas for the Pf caps
Then use ceramics.
Or polystyrene caps ($$$). Downside is you better have good soldering technique; get on, get off.
I really don't want to use silver micas for the Pf caps ... problem is I can think of anything else to use apart from dominoes ...
The "dominoes" were almost always mica caps, albeit with a different construction and outward appearance.
Still undecided on the ... mustard ... caps, I absolutely love the sound of old non top boosted jmi's and would like something that will help achieve the same! ...
I don't know for sure, but "mustard caps" probably have a polyester dielectric given their size/capacitance ratio. If it were me, I'd pick a polyester film & foil cap. Otherwise, pick whatever makes you feel good.
The speakers and output transformer will probably impact the sound more than the coupling caps.
Would anyone advise against carbon comps?
The original amps used carbon comp resistors, though the particular manufacturer used a white background color instead of brown. If you want to use them, go ahead.
My preference would be for metal film, but for reduced noise and not on the basis of tone. I'd probably use wirewound for lower-resistance, higher-wattage parts for the same reason; wirewound resistors have the least self-noise, followed by metal film.