Doesnt matter if its Atmos or something else, they all do the same thing. If you feed Atmos the information of the object, it can do the same thing as a natively integrated hrtf, if you only feed it the information of the speaker, it will visualise the position of the speaker. But yeah, there arent really many games that support Windows Spatial Audio, so with most games it will end in a 7.1 speaker simulation.
If you plan to play in (Lan-)tournaments you probably cant use any of the software, no matter if its HRTF or EQ, so you will just have to live with what the game gives you natively anyway. But when your planing to do that, you probably wanna just use the same headphone (which is probably a IEM or closed back one) even for home playing. Consistency and getting used to the sound of your headphones and the game is important, so i wouldnt even be using open back heapdhones at home if playing in tournaments is the goal.
If you think Warzone is bad, you should hear the sound design of Vanguard, footsteps in this game are literally non existent. 
Yes, they definitely add EQ. Thats why i personally didnt like Dolby Atmos for Apex myself, it added too much Bass for my liking. After trying out several different programms, i ended up with HeSuvi and its oal.dflt preset, that works the best for my ears. Even tho Apex still only offers a 7.1 speaker emulation, that setup massively improved my ability to locate sounds in this game.
A game always has to use some kind of hrtf to even place sounds, otherwise we would just get mono sounds in each channel, which would make it basically impossible to locate anything properly. But developing a HRTF sound will cost a lot of time, money and effort to do it properly, so its just easier and cheaper to keep it simple, its simiar if not the same as modern music or movies are mixed. This maybe is more consistent with different ears, but it in the end it never can be as acurate as a proper done hrtf, if the hrtf matches your ears.
Its also a lot easier for gamedevelopers to keep it simple, since you wont hear the difference of placement that well anyway. One example of that is Counter Strike when it introduced its hrtf, people complained that hrtf makes the game sound worse, especially the knife sounded muffled. Reason for that was, that the devs placed the knife sound on the players feet instead of its actual positon. You couldnt hear that with the old stereo sound, because the simple stereo just lacked the ability to place sounds vertically. So devs actually will need to have work more precisely, if they choose to implement a proper hrtf solution.
So, in terms of being able to tell directions, HRTF will always be better than a simple mix done for stereo speakers. The science behind HRTF is solid, a hrtf signal has way more location information than a simple stereo signal, its just a matter of how good your brain will be able to “decode” that location information. Lets assume that the used HRTF matches your own HRTF 100% (which is unrealistic, i know) than you will get a big advantage over somebody who doesnt or simply cant use it. The question is, how good the generic HRTF has to match your ears to be an improvement over the stereo mix the game offers.
Another problem is that people dont know what hrtf is and what it does. Some people will probably even claim that simple stereo is better, even if their game is using hrtf, simply because they dont know better. I love it when people claim “stereo is always better” and then linking the virtual barber shop on youtube as their proof, even tho the video is a hrtf recording.
I personally see “stereo is better for competitive” as minsinformation, because most people dont even properly know what HRTF/Virtual Surround even is, so when its mentioned i would personally rather have the advantages and disadvantages of it explained so people can make a choice with the best information they have.
Maybe i have been too opinionated because it just seems to really work well with my ears. I tried to find some studys to see, if there is a % of how many people are compatible with generic hrtf models, but i didnt manage to find any. I found something that it is possible to adapt to a different HRTF than your own in a VR environment, but even that didnt really have any consistent results. It would be interesting to know, for how many people the generic HRTFs actually work, and for how many it doesnt.
Since soundstage/imaging is mostly a HRTF created by the tuning/phsyical build by the headphone itself, it could indeed interfere. I dont think there is really any research about this, so i only have my personally expierence, but in my expierence bigger soundstage (with bigger i mean something like the AKG K702, i havent personally heard something super wide like the HD800s yet) acutally improved my ability to tell directions with hrtf. Narrower soundstage heapdhones like the HD660s were not that great, neither in stereo nor with HRTF, but HRTF did improve them a bit in my case. That is however just how i perceive it with my ears, that could be different for other people.
I think we generally have to be more careful with claims about headphones for gaming. I often read stuff like headphone A has better imaging than headphone B, that can be true for the person using it, but other people could perceive that differently.
There still seem to be consistent opinion about headphones, i think most people will say that the AKG K702 or HD800s will sound wide and something like a HD6XX sounds narrow, but people still have contradicting opinions about Soundstage/Imaging all the time, the most recent one is probably the “PC38X has best imaging/soundstage for gaming” recently spread by DMS, which a lot of people here disagree with.
I think there are so many factors to consider, to make such claims. Alone the unit variations of a headphone can change that, that is probably less a problem for High End headphones like the HD800s, since they seem to sound pretty consistent, but stuff like a Beyerdnamic Tygr, DT770/880/990 seem to have quite big unit variations.
Then of course our personal HRTF and the game used (and if the game is used with or without hrtf sound) play a huge role as well. So i think the most consistent method right now would probably be to actually to record the gameplay scene, to showcase where a headphone performs better and in what way it performs better. I think that is also a pretty good way to check ourselfs, if really the headphone we used gave an improvement in that one situation, or if just the gameplay situation itself made it really obvious where something came from.
We shouldnt forget that a lot of gameplay situations differ from each other, so we are unlikely to have the exact same situation twice in a game, so is it really the headphone which made it easier to spot something or was it just placebo or the game itself? I had a lot situations in the past where i felt like, wow, i wouldnt have heard this with another headphone, but after checking the gameplay recording that wasnt the case, i could hear it just fine with most headphones.
To come back to HRTF, even tho the tech is by far not perfect, and there are so many aspects on how it is not ideal, im still always surprised, how well it works with my ears. In this video for example, the HRTF version is just so much better for me than how the original game engine would play it.
