Ultraportable AMP+DAC with a mic pass-through?
So i've been wondering if there are any and if yes, which is considered good and which not? Are they even worth it in the first place or you'd rather not have a mic to use (will probably be used with a phone as source and i don't want to lose the mic/remote feature on the headphones).

Oct 30, 2019
If you want a dongle, the Venture Electronics Odyssey HD supports mic pass-through. The Shanling UP2 also has a microphone of its own, so you can use it to take calls even if the headphones you are using do not have a microphone.
Oct 29, 2019
The new FiiO BTR5 comes with in-line mic support and control. Hasn't shipped yet, but ought to be available in the next month or so.
The Creative line is about the only ones I'm aware of with any consideration for Mic support. In-line mic/controls can be a small source of noise with headphones/iems so many amp/dacs skip this feature. With your goals in mind, assuming you aren't on iOS, I would go with a Radsone ES100 BT Amp/DAC. With Android O and LDAC BT support that device sounds almost as good with my Noble K10 as it does wired from my LG V20. It also has a built in mic that works well and the BT controls work with my devices (play/pause/forward/back). iOS only supports AAC which IMO sounds better than base bluetooth codecs (SBC) but not as good as aptX, aptXHD, or LDAC (all supported by the ES100 and my phone).