You would probably want to use an SPI DAC in that case. There are many options at various bit depths (from 12 to 18 bits) , both single and multi-channel. Most are surface-mount, but a few through-hole DAC chips still exist.
You should be able to use the PITCHBEND & MODWHEEL pots exactly as wired. PITCHBEND usually has some mechanical mechanism to return it to center when not activated, so I'll assume that this is the case in my functional description below...
The bill of materials and build guide is online if you want to source yourself
You could also try a kit, with all smd soldered already
If you plan on using...
No matter which kind of cable or PCB is used, be careful about the total power supply capacitance if it will ever be hot plugged. The Teensy 4.1 design assumes a SD card with very little capacitance. If you have several uF power...