Welcome to the forum @leer10! Yes you really need to solder the screen in place or at a pinch, solder header sockets on the TBeam for the screen to connect to. You are right though, you can find the bluetooth pairing code within the debug output but it is easier with a screen.
The most common is a 0.96" OLED using an SSD1306 driver I/C. Ideally you need to find one that the pins are labeled VDD -1, GND - 2, SCK - 3, SDA - 4. This way they line up perfectly with the TBeam pins without further soldering!
I went with a slightly larger 1.3" white OLED with the correct pinout. Here is an example. https://www.aliexpress.com/item/4000191763740.html?spm=a2g0s.9042311.0.0.27424c4dv0uDB6
I’m unsure on 18650’s in the US (I’m not there) but unprotected cells fit best in the TBeam. Any 18650 that mentions protection is a little bit longer and a bit of a squeeze.