Can this be used also as an amp only through the se in and 4.4mm balanced out?

No. You should be aware that the 3.5mm and 4.4mm connections are headphone outputs, never inputs. The input is USB only. Think of it as a dongle, but flat and with a battery, for use with a mobile phone, but with improved ergonomics.

Oh well already bought and it’s on the way, doesn’t bother me the usb output though

Ok got it this morning and tried it now with a couple of songs.
First of all I gotta be honest with you I’m impressed.
Compared to my fiio q3 mqa this not only is smaller but also more powerful, I love it so far, I’ll be getting the topping nx4 in a few days and will compare the three.
Cheers!
Edit: after using them for about 1 hour I noticed it gets quite hot, this overheating problem the fiio q3 doesn’t have.
Must be the tiny size but it’s really disappointing.

Smaller size and more power means more heat dissipation, of course. It's also true that I don't worry too much about it, because almost every DAP, dongle and DAC/Amp I own gets hot. That's why I don't usually comment too harshly on that aspect. It will be a point to comment on for future reviews. Thanks for your note.

Yeah, compared to the fiio q3 I use it at max volume on medium gain and max volume on the fiio on high gain (fiio only has low and high gain) and the volume is about the same but if I want that extra volume I go high gain on the hidizs but only for a couple of songs.
On a second thought I use the fiio as an amp with 3.5 to 4.4 I don’t use its dac capabilities at all, that’s why I was asking if it’s possible for the hidizs to do the same.
Now that I think about it if I use the fiio through its usb to go dac mode it might get hot just like the hidizs… I’ll try this when I’m back home after work and report back.

Ok after spending a fair amount of time I can tell the Hidizs is not good… it has all the potential but it just isn’t good enough.
Apart from the device overheating (something that doesn’t happen with the fiio even with dac mode) it also has a lot of distortion.
If you for example listen to Heavyweight by Inflected Mushroom at medium gain full volume you can clearly hear the distortion at the beginning of the song but it’s at the end where you can hear the horrifying distortion, let’s say the last 25 secs of the song, the outro.
I’ll be selling the hidizs as it may suit iems or people that are ok with distortion.
A very sad end

It is strange what you say. In a review with quality measuring devices, there is no mention of distortion. It only says that with very sensitive IEMS there may be noise.

https://www.audiosciencereview.com/forum/index.php?threads/hidizs-dh80s-review-dac-amp.27942/

Have you tried talking to Hidizs technical support?
Could it be a faulty unit?

Couldn’t be bothered, I don’t think it’s faulty, it’s sold anyway.
If you still have the device can you try that song and check it out yourself? I think that’s the best way to check if it’s only the unit I have or all of them.