A couple of minor comments:
1) Pin 6 is used by the audio shield if you solder a flash memory chip to the audio shield (which can be a faster but smaller permanent storage device than the SD card). Even if you don't solder in a flash memory chip, it might avoid problems if you use a different chip for the CS pin select.
2) On SPI systems that have multiple devices on a single SPI bus, it can be helpful if you have pull-up resistors on each CS pin. Note, the audio shield adds pull-up resistors for both pins 6 (flash memory) and 10 (micro SD card reader), but you may need one for your display.
3) As the paper above mentioned, some devices no do properly handle tri-stating. On the Teensy 4.0 you could move the display to the second SPI port, but you will need to solder 2 wires to the pads underneath the Teensy. Note, pin 1 is MISO1 (it isn't on the pinout card unfortunately), which means you would have to re-route the MIDI connection from Serial1 (i.e. pins 0/1). I think you can buy tri-state buffers also, but I don't have any experience with this.
4) You aren't hooking up the reset pin on the display. You might want to hook it up to a pin, and explicitly reset the device when needed.
5) I've read about different ways touch sensing are communicated. If it uses I2C, it should be ok, providing you don't use the two I2C ports used by the audio shield. If it is a SPI connection, I recall some of the devices in the past had trouble with tri-stating. I've never used touch screens in my usage.
6) Generally, I try to do hookups, etc. on a breadboard first before moving to a soldered connection. That way you can verify that it works first, and possibly move pins around as needed before going to solder. If you go straight to solder, it could be you need to change pins, or it could be your solder connections need to be fixed, so it can be harder to figure out what the problem is. Of course the downside is, I've had ports on breadboards stop working, and using cheap jumper wires can sometimes stop working also.
7) Particularly on a fast Teensy like the 4.0, you can overwhelm the display by sending data too fast. It may be helpful play with the SPI bus speed if you display is glitching. I've found that even for the same driver, different manufacturers displays might top out at different SPI bus speeds.