You can debug the heltec wifi 32 v2 using the esp-prog jtag debugger and the eclipse/openocd debugging tools. See the expressif website. I have it working.
Unfortunately Heltec have connect the OLED sclk pin and SX1276 reset pin to the jtag lines which means you cannot debug an application which uses the SX1276 and OLED.
Please please please Heltec could you change these pins? Even if you only change the SX1276 reset connection this would mean you can JTAG debug applications and use the SX1276.