Parallel is the recommended place to begin.
FWIW, I always start with top of headshell parallel to platter surface and if necessary adjust up or down in tiny increments (<2mm typically) if need is perceived. And yes you can do this by ear.
👍 - Unfortunately, not all arm tubes are on line with their cartridge mount - where you’re trying begin as @lewm mentions
Potential pitfall 2.) Many tonearms create VTF changes for the cartridge/stylus when VTA is adjusted - be aware of what you’re listening to/for
Cartridge setups are a combing-through process that should finish in most cases as a “set & forget” with all the variables in-the-window 🎶
If differences are not experienced, then just go for a technically correct setup and call it a day.