Headphone jack has been a hard line for me. Having recently moved into the world of wireless charging (I keep a phone 5-7 years and just missed wireless charging being normalized on my last phone purchase back in 2020) I think using the USB port for headphone is finally visible.
I spend a lot of the day with my headphones on and the phone on the wireless charging puck. Not being forced to choose between charging and headphones changes the equation.
In this post headphone jack world I use a fiio Bluetooth/USB DAC that's really good quality. But it's about the size of two ipod nanos stacked on top of each other.
Not necessarily. If the device is using audio over alt-mode, it can use its own DAC.
FWIW, audiophiles were very impressed with the measured performance of the €10 Apple USB-C to 3.5mm adapter and its DAC. The Google one is likely good too.