Thanks for sharing all the insights. The undelete tip is excellent! Are you using the Endurance MicroSD for only dashcam/Sentry or also for music? If also for music, are you saying that the music partition mounts quickly?
I'm only using the sdcard for sentry. I could try one for music if you would like. Oh yes. I always have at least one spare dashcam/sentry storage device. The plan is that if an incident happens and I remember then I will turn off the dashcam, remove the device and then put in a spare. This means mucking about with undelete is plan B.
I had many years experience working with usb storage devices while developing a fast booting version of Linux that runs from usb sticks. IMO the speed of the devices we're discussing will have almost no impact on the time it takes to mount. OTOH the speed of the device may be an issue if you have many thousands of songs because the car needs to scan them all to get title, artist, etc info.
The read speed of the Samsung bar that Tesla provides is 3 times faster than the Samsung Endurance Pro sdcard. The amount of information needed to mount a file system is so small that this won't make a difference. If you have a lot of music then the bar will theoretically scan it all faster. But Tesla says they only support usb-2 which is 10 times slower than usb-3 so faster usb-3 device won't help you.
The Endurance Pro should max out the bandwidth of the Tesla usb port (assuming I did my conversions correctly). Perhaps the best thing you can do for speed is to enable the center console data feature so dashcam and music aren't sharing the same device/port.
Maybe you've explained it already, but could you describe the delay you're experiencing? For me, the music device seems to mount very quickly. But this is after the car is already awake, usually due to enabling climate control from my phone. When I unplug and replug the music device I'm surprised by how fast the usb music UI pops up.
When I first tried usb music I copied my entire collection to a usb stick which was a big mistake because the UI is so terrible. I now limit myself to well under 1,000 songs. If you have a lot of songs then there may be a delay while the car reads them all to get the artist, etc information. I organize my songs by folders and file names (2000s or earlier technology). This allows me to control the organization and even create crude playlists. I try to make it so each folder level mostly fits on the screen so I don't need to do a lot of scrolling.
You can use multiple usb music devices. At the top level the car will ask you which one you want to use (at least in folder/file mode).
[Sorry this is so long and partially redundant. I'm typing past my bedtime.]
