My JP-2C has by far the best cleans of all the amps I’ve ever owned: Revv Gen 120 MK3, EVH5153 100w 6L6, EVH5153 50w Stealth, Fender 68 Custom Vibrolux Reverb reissue, Peavey JSX, B52 ATX100, Jet City JCA20H, Wizard MTL MK2 100 E34L
I’m definitely a fan of the Creamback H75 and it does sound the way you described in my 212 cab. I also have a 112 cab with the WGS Retro 30 and have swapped it back and forth with the H75. For me the H75 is slightly better with a bit more presence than the Retro 30, but both are great speakers.
5751 will give you more headroom and a cleaner sound. I believe you need to go in the other direction. Try a NOS RFT 12AX7 that tests higher gain than normal in V1 for earlier breakup.