Questions about Creative Sound BlasterX G5

I wouldn't buy it at all, it has terrible driver software. Better to get one from Fiio.

I just tested on xbox one. - Voice chat does not work with this device. - The Sound Blaster X G5 is only compatible for game sound via the supplied optical cable. But I notice that the sound is less amplified than connecting directly to the controller (even with the volume turned up). - The Sound Blaster X G5 is not compatible with the 7.1 audio format, but it does have a basic format that simulates 3D sound. To sum up, according to my test, I would not recommend it for use on xbox one. Because it is not fully compatible. On the other hand on PC and PS4, it works fine.

Yes, the DAC improves the audio of the microphone. (Noise reduction and voice enhancement). However, this is only really noticeable with a bad microphone, if you have a good microphone it is hardly noticeable. (Your voice can also be changed, e.g. robot voice, male to female etc.).

Beyerdynamic Custom Studio (Over-Ear, Black) What about these? Are they also good for gaming? Because I heard that you can connect a microphone here or should I get the Modmic?

No, the Creative Sound BlasterX G5 replaces a sound card. Either you have one internally or, as in this case, externally. In my opinion, a combination makes no sense at all.