In simple output mode, it is hardcoded that if you choose nvenc, OBS will first try nvenc (new), and if this isn't supported by the chip, it will fallback to the old nvenc implementation. You can see which variant is actually used if you do a recording in simple output mode and look at the logfile afterwards. If you see the [jim-nvenc] encoder was actually used, OBS detected and used the (new) variant.