I mean it is a bit of an ignorant post. A little bit research would answer OP's questions.

Absolutely. But you have to know what you want. Being able to test out headphones is a good idea. Most of the time though it's a "sidegrade", finding the sound signature and tuning you prefer. As much as I like my HD650 there are noticeably big differences between my more expensive headphones, such as bass extension, soundstage, imaging etc.

Qobuz + Roon (or Musicbee) for local files.

Not having to deal with room acoustics, not bothering others, it can be more immersive with headphones, hearing music in a different way, easy to change headphone if you're in the mood for a particular sound signature/ tuning, they take up a lot less space, personal preference etc.

There is no "x is better than y", it depends. If I want physical impact and a wider soundstage I listen to speakers. Most of the time I just enjoy headphones.

ZMF Atrium Closed is coming soon and sounds like it would be right up your alley. Looks like it'll have elevated sub bass compared to Atrium Open and Verité Closed from the few impressions out there. I haven't heard any of the ZMF yet but got Atrium incoming. My favorite (so far) is LCD-X 2021 with EQ, a nice bass shelf and they sound amazing to my ears. TH900 got the most bass stock out of any headphone I've heard but they're way too bright on a lot of songs.

Sennheiser HE-2

When I really want to get into the music I just sit back do nothing. I also enjoy music with games where I don't need to hear the game (on mute).

I got it a couple of months ago and it's one of the best audio purchases I've made. Not that it sounds any different from my older Burson Conductor, but I was starting to get some issues with the Burson which is why I bought the RME. And the amount of features. Nothing on the market comes close, especially in this price range.

The menus are a bit clunky at first, but once you get used to it it's super intuitive to navigate. I have individual PEQ profiles for all my headphones and it drives anything with ease. The remote is great and the quick access to treble/ bass was something I didn't think I would need as much as I do. If you use Crossfeed you can bind it to the remote so you don't have to go to the menus every time you wanna enable/ disable it. It's truly a "end game" DAC, whether or not you believe a quality DAC can change the sound.

That sucks. I've only had good experiences. Owned the LCD-X for almost 2 years now with heavy usage and they're still in excellent condition (as should be expected with mostly a metal construction). They also sent me frequency response measurements months after purchase.