How and where can I see and use all those settings ?

Here is the solution of the riddle.
My comparison was a kind of a joke, because I can do the same in VPro 15 without any change in settings of that program, so it must be a bug or something that Magix should warn for before to use that option.
Maybe the developpers can build this option into that Intell HEVC codec.

The only thing I have to change is the setting for my videocard in Windows Device Management to disable my Nvidia videocard.

This video also shows my laptop which has more possibilities for making this very fast rendering possible in the option which GPU has to be choosed for starting a program.

See this video for the two different renders with the same codec without making in the program any change.

Be sure you click that "customize template" button and make sure that the settings inside the preset are all the same... That is where you choose if you are using your GPU, intel quicksync, or CPU only. Quicksync runs off the CPU (built in GPU to some Intel CPUs, more accurately), which is why I was asking if somehow that may have been enabled in Vegas 15, as that was a feature they added to version 15 that was supposed to speed up encoding of HEVC and H264 files. That said, I wouldn't put it past it just being a bug. If so, good catch.

@fr0sty I don't believe you have any such "Encode mode" choices in the "Custom Settings - Intel HEVC" dialog (unlike in the various AVC dialogs). Vegas should just use QSV if it's available. See this comment from a Vegas developer.

There are some weird and complex things going on in recent VP15 builds with regard to QSV and NVENC. Hopefully they will be resolved in the next update.

See this comment from a Vegas developer.

In the following comments that developper asked about 10 bits HEVC rendering.
With me, both graphics allowed and very slow rendering it is no problem to render 10 bits Intel HEVC.
But with only the Intel GPU allowed I get an error trying to render to 10 bits.

Therefore I think the difference in this topic is caused by my impression that in my normal situation ( both GPU's available) the Intel GPU not is being used, but the rendering to Intel HEVC is all by the Intell CPU and in that case Vegas don't uses QSV.

@Vliegvisser This is all meaningless if you do not have a monitor connected to your motherboards' interface (to be able to use INTEL QSV for HVEC, and obviously have it enabled in BIOS, and have an INTEL processor with GPU inside not all INTEL CPU's have this).

If you use a laptop chances are big you can use it for obvious reasons (a screen is usually build in 😀). If you are on a desktop with a very big ultra wide screen, I have no space on my desk left for a second screen. I am not going to castrate my video computing power from my nvidea 1080 ti to the INTEL GPU just for encoding. Connecting my screen to the intel just for encoding is in my particular case also a practical nightmare as the peculiar way I have build my own PC for the airflow and the way it barely fits in my desk's wood cabinet.