@funkybro, Hi, welcome to the forum!
Thank you for providing links to your devices in question. This helps for providing answers.
I assume you have already read How to get the best out of this forum.
But I regularly post that link to my first answer to new posters.
Just to make sure, this black/white 400x300, 4.2inch E-Ink display module is your display? And you got it complete with the colored connection cable.
Unfortunately I can't help you with your Heltec OLED module yet; this has been asked before, and I bought one, but I didn't try and solve its use with e-paper displays yet. I think they use non-standard SPI pins. I will try when I am less busy.
Your Universal e-Paper Raw Panel Driver Board, ESP32 WiFi / Bluetooth Wireless should work with the suggested wiring for ESP32 with GxEPD2. Just remove the flat cable from the driver board, and connect the colored wires to the appropriate processor pin. Check the connections, there may be bad DuPont connectors, and push the white connector firmly in.
See README.md for use of shortened reset pulse most likely needed for this board.
Use e.g. a board like WEMOS LOLIN32 to compile for, as ESP32 Devkit may cause hang on Serial.begin().
If you ever want to use the driver board additionally connected to a raw panel with the flex cable, you would need to use a different wiring, as the flex connector doesn't use the standard HW SPI pins. See example GxEPD2_WS_ESP32_Driver.ino
Jean-Marc