For headphones take a look at the HD560s, very neutral and flat sound which is great for music production and super cheap atm around £139. Some say they are better then the HD600 in terms of neutrality, HD600 is highly regarded by many top mastering engineers so a great choice IMO. They released the newer HD400 Pro which is the exact same drivers just different cable, check the review on youtube for those and see how they compare to high end models like Audeze which are much more expensive. I have a pair and was able to drive them okay from a cheap Focusrite Saffire Pro 24 (relic from 2007), Recently I have been using them from my M1 MacBook Air's headphone output which really tranformed the sound of these headphones and drives them louder than I need so any recent budget interface should be able to drive them fine. There is also some corrective EQ settings available in the review video which I use, I find it improves things even more and ever since my mixdowns always translate on my studio monitors with not much effort in the mixing process. Goodherts CanOpener is a must have for using headphones, this re creates the crosstalk you get from listening to a stereo pair of monitors. I don't always mix with can opener but it does make things sound more natural. My only hate for the Hd560s is the awful long cable they include which always gets tangled, you will want to get a cheap replacement cable from the rainforest site for £10.
For interface I recommend the Motu M2, it is £174 so slightly more expensive than a focusrite but much better AD/DA converters/clocking and the heaphone output is meant to be very good. Motu is fairly stable on MacOS with their drivers, that will be my next purchase for my new M1 setup.
If your not recording any analog inputs you can honetly get away with using Apples Core Audio driver and the Mac Studio headphone output, I had the M1 MBP16 which has the same output and it was very good in terms of power and sound quality. Latency may be slightly higher but with the M1 you can keep the Buffer size very low compared to Intel CPU, before I would have to run 512-1024 but now I can run a whole project start to end at 256. Increasing the buffer on M1 does not make the biggest difference, sometimes the CPU performs better at lower buffers depending on your DAW. The input latency with MIDI up to 256 Buffer size in not noticable to me on my Air, so I'd say give it a try before you buy an interface.