Camco and RVGuard are both well reviewed/rated brands with a decently long track record of providing good products. Many people will say to never use an extension cord; generally safe advice but sometimes unavoidable.
As with all high amperage/high voltage things, you should load test them under observation for 1-2hrs. For example, when I had my Grizzl-E installed with the outlet, I plugged the car in and allowed it to charge for 1-2hrs while I organized/cleaned the garage. Every 20-30mins I went over and hit the outlet with an
Infrared Thermometer (which is also super handy for ensuring proper griddle temperature for pancakes and bacon !) to look at temperature increase of the outlet, conduiting, power cable in, and power cable out compared to ambient wall 2-4' away. I also handled the cables to feel for hotspots. The outter jacket was rated to 105*Celsius and the cable never got above 35*C/95*F (if it's even accurate/properly calibrated. Regardless, I noted a 15*F temperature rise compared to the wall so even if the numbers aren't accurate, the delta between ambient and cable should be accurate enough).
The electrician did mount my outlet either upside down or rightside up depending on how the grizzl-e wanted power. You could look at flipping your outlet upside down ?
