I tested a lot of headphones and the DT 880 were the best in comfort and soundstage from all of them.
The problem is though I would like to EQ them to have boomier bass and sound warmer but I don't know if that will make them sound worse or if there are other headphones that fit my taste? Or is it save to EQ them without distorting the sound too much and making them sound bad?
That depends on whether 1) you have the right EQ with the right tools, ie, it can target the correct frequencies and 2) you know how to do that, and finally, 3) there's really no telling if
you will like the result if so. For the first two, I can give you an EQ profile that you can input into programs like Neutron Music Player or any other variable software EQ like Equalizer APO.
Neutron Music Player
Subsonic Filter : On
Band 1
Filter Type : Low Shelf
Center Freq : 30hz
Q Factor : 1.0
Gain : +5dB
Band 2
Filter Type : Peak
Center Freq : 85hz
Q Factor : 1.4
Gain : +2dB
Band 3
Filter Type : Peak
Center Freq : 6,000hz
Q Factor : 1.2
Gain : -2dB
Band 4
Filter Type : Peak
Center Freq : 9,000hz
Q Factor : 1.0
Gain : -6dB
Band 5
Filter Type : Peak
Center Freq : 10,000hz
Q Factor : 1.2
Gain : -2dB
Equalizer APO
Band 1
Center Freq : 20hz
Gain : +6dB
Band 2
Center Freq : 30hz
Gain : +3dB
Band 3
Center Freq : 85hz
Gain : +2dB
Band X (It's a graphic EQ so check what's closest to this freq and replace that)
Center Freq : 6,000hz
Gain : -2dB
Band X (It's a graphic EQ so check what's closest to this freq and replace that)
Center Freq : 7,000hz
Gain : -2dB
Band X (It's a graphic EQ so check what's closest to this freq and replace that)
Center Freq : 8,500hz
Gain : -6dB
Band X (It's a graphic EQ so check what's closest to this freq and replace that)
Center Freq : 10,000hz
Gain : -2dB
As for the third point...that's where it gets tricky. You could at best tweak the gain on these settings and see if you get to what you want, but of course, no guarantees. EQ of course is deliberate distortion to the source signal or the input signal to the amp (in the case of bass boost controls and analogue EQ units), so the chances of a boost to the signal causing actual, easy to hear, bad even in subjective terms driver distortion is a real possibility, which at minimum could be kept in check by having an amp with a lot of power and very high damping factor. That still doesn't guarantee you'll get to what you want though.
That said...what were the conditions when you tested them? If there was reasonable noise (my room during weekend afternoons with the windows and door open, door to balcony on the hallway open, fans, no A/C running yet) has a noise floor of about 50dB. Any open headphone, even my HD600 EQ-d to mimic the HD650, will not have enough audible bass in there. If the place you tried the headphones on was in a mall and there were enough people around in the store or even in the hallway and you weren't in the isolated listening room, the noisefloor would likely be comparable or still problematic. You can't hear enough of the bass and crank it up to try to do so, making the 9,000hz peak on that headphone even worse (and it's already objectively bad).
Lastly, considering what you want in the sound, have you tried the Sennheiser HD650? You can get the Massdrop HD6XX version. The variable here though isn't just sound but also comfort, and in the end, you have to be the one to weigh the risks.
One thing that could make it easier for you though is to go back to where you tried the DT880 and use a device running either software I mentioned with the EQ profile I provided. If that sounds good enough to you, then might as well get the DT880. Make sure you run it through an amp though because I have a fairly aggressive boost on the bass.