SD cards are always going to be slow but looking for the "A2 Application Performance Class" it will give you a tiny boost in "IOPS which is the most important metric for responsiveness.
The crap shoot of SD card quality along with the headache of having a universal file system if you did remove the SD card has made it go the way of the dodo. Modern phone storage being significantly faster also didn't help things.
SD cards are always going to be slow but looking for the "A2 Application Performance Class" it will give you a tiny boost in "IOPS which is the most important metric for responsiveness.
Source: https://en.wikipedia.org/wiki/SD_card#Application_Performance_Class
...however I don't believe the Pixel 6a has an microSD card slot to begin with.
Source: https://en.wikipedia.org/wiki/Pixel_6a#Reception
The crap shoot of SD card quality along with the headache of having a universal file system if you did remove the SD card has made it go the way of the dodo. Modern phone storage being significantly faster also didn't help things.