I’m someone who probably spends too much time behind a screen, so I’ve spent a good time reading about ergonomics and fiddling with my setup, all in the sake of not hurting myself by sitting haha.
Optimally you want to be able to reach your keyboard, where your elbow is as a 90 degree angle. If your “reaching” for your keyboard, it sounds like your too far away from your keyboard and should bring things closer. If things are too close, your elbow would be forced to be more “behind” you, which is also not ideal.
Gaming chairs support similar function as something like an office chair, which is longer sitting sessions. However, I suggest doing your research as not all gaming chairs are made equally. Its also possible your paying for the “flashiness” of the gaming chair, and not getting adequate support for a given price point you could get with a more traditional office chair.
The only other suggestion I have is investing into a chair with adjustable arm rests, the rest of the features should be more to your liking (like support for leaning back). Armrests will allow you to be more flexible with your own setup, where you can rest your elbows on the armrests, or adjust them lower than the table, get closer and use the table as your armrest. Having that flexibility is always nice.
Odds are you will want to leverage the back of your chair, optimally with some kind of lumbar support. Otherwise you will end up slouching due to not having a back rest.
Leaning back is more something you’d want to leverage as a “nice feature to relax”. Perfect for situations where you want to lean back and think, but less optimal for working in such positions. The reason for this is due to the effect “leaning back” all the time has on all the other properties of your setup, suddenly your further away and now are “reaching” for your keyboard, things are “lower” so your bending you neck, and finally your legs could be anywhere from bending a lot, flailing around, or doing random stuff. Its fine to get some stretching in, and giving yourself a break from the same posture, but not something you’d want to stick with all the time.
There are many chairs and manufactures out there. Lots of people only get a chance to sit on a few, so most advice is usually anecdotal. I suggest looking for chair features at your given price point, and then reading reviews/comparisons around that chair. This way you can get an idea of what your getting for a given chair, and missing out on relative to the competition.
I personally sit on a Herman Miller Logitech Embody chair. It has served me well during work-from-home, however I wouldn’t suggest it due to its extremely high price point, and a few issues relative to its lumbar support being somewhat unforgiving.
Desks are easier as they really only fall into 2 categories.
Adjustable would be any kind of desk that can change heights, this includes standing desks, and some desks that support adjustments to their height.
Obviously having a standing desk removes the need for a chair, but odds are you will still end up sitting often, and standing desks allow you to adjust the height of the table relative to your chair. This gives you a lot of flexibility to get your entire setup the right height.
If your table isn’t adjustable your more “stuck” with whatever height, and thus must adjust the rest of your setup accordingly. For some people this could mean their legs don’t touch the ground if they are too short, or if they are too talk, end up with their knees bent. This is of less concern compared to how your upper body and back are setup, but it is worth keeping in mind.
Finally there is one other aspect of your setup worth analyzing, and that is your monitor placement. Since it sounds like you have a Macbook, and a “mounted” monitor above it, odds are your close to optimal. The recommended setup for your main monitor is the middle of the monitor is slightly below eye level, and at arms length. The purpose is so your neck is as straight as possible as often as possible.
If you use your laptop monitor (which is lower) more often, you run the risk of hurting your neck by looking down all the time. This is a big reason why working long periods of time on a laptop isn’t optimal. This also ends up making you want to slouch, to “get closer” to the monitor, and if the monitor is lower, you will have a bigger tendency.
The overall goal of this is to have your feet flat on the ground, your knees bent at a 90 degree angle, your back supported by your chair via lumbar support, your head straight and arms in the positions I mentioned earlier, with the monitor at the optimal distance and height.
If your setup supports this position, you will be in the recommended position for sitting long term, which is the currently understood most “optimal” ergonomic setup.
There are a few aspects I didn’t cover, such as keyboards and mice optimization, but if your using a laptop you can’t change those anyways, and they are of less importance than how your sitting.
Finally, there is something you can do now. That is get up and walk around/stretch often. If your sitting for 4 hours straight, its easy to get a “kink” somewhere and feel horrible. Its recommended to get up and move around at least every 30 minutes.
I personally kill two birds with one stone, and keep a refillable water bottle next to my desk that I drink often. This helps me stay very hydrated, while also forcing me to get up and walk to the bathroom often. You might have something as simple as just a timer you set for 30 minutes to re-adjust, stretch and just “reset” your body so its not stuck in one position that may be bad for you.