Yes I Have the FONT_RAMP hack on my PW3 but, of course, with KFX it doesn't work. It's only a question of individual preference, we can't have all, sometimes I would need an intermediate size but I still prefer hyphenation, kerning and ligatures when reading.
And the KFX output plugin of calibre doesn't work with Linux, but I have a dual boot with Windows 10, so I use calibre in Linux for Kobo and calibre in Windows for Kindle. Life is complicated