As I recall, chat is always through the controller on PS4, regardless of how you're getting game audio to the headphones 

That could be wrong though, as I don't play online on my PS4 anymore   So, my knowledge of chat there is out of date and/or I may be confused.  

1) I will always believe a proper set-up will always win over the simplicity of the Soundbars if we compare premium with premium however that's mainly because Home theatre systems can exceed the Soundbar price range by big amounts. The most expensive Soundbar iv seen cost $2k, iv seen Theatre systems cost in the $4k ball park. However a good quality Soundbar itself can outperform the front/left/right speakers of a Theatre system due to there massive size, the amount of Speakers built into them and they are actually design to deliver amazing clarity and quality from the front. In terms of surround sound, than a 7.1 Home System vs a 7.1 Soundbar than the Home System will deliver the better surround sound. I think Soundbars can come really close in comparison especially the new range of flagship models in 2018.

2) Cheap Soundbars are glorified TV speakers, I will agree there, however premium models do more than just mirror Surround Sound. I think you should listen to a top of the range model and hear it for yourself. I use to think Soundbars are crap as well, until I heard what they can actually do. 

3) A couple hundred dollars wouldn't be anything amazing. You can also buy cheap home theatre systems dirt cheap that would sound crappy as well. Cheap speakers are cheap speakers after all.

Always wanted a surround system, but i have neighbors to consider so i stick to my TV-speakers which aren't exactly the best.

Optical audio is also limited to 2.0 uncompressed or 5.1//7.1 lossy compressed. Same as HDMI ARC.

I use both the amp and the tv for inputs, too many devices, not enough ports on either. Combined it works!

I spent probably a couple hundred bucks on my 5.1 hifi sound system for my PC. Yet to hear a sound bar that produces higher quality audio... And that sound system is probably 10+ years old.

So I am not speaking directly from ignorance here.

When it comes to 3D positional Audio, sound bars just cannot compete.

You aren't wrong.
With that in mind... Toslink allows for upto 125MBs of bandwidth... Keep in mind that it's software layer is based upon S/PDIF and generally it's the cable that really differs.
In short, can still do 24bit/192khz over 5.1 (Although the DSP is 48bit, I am not enough of an Audiophile to actually care). - Don't really notice the difference with regards to compression, I can't tell the difference between CD and a high quality MP3 encode either.

Hearing you on the lack of ports. Having the NES, SNES Classic, Xbox, Xbox 360, Xbox One X, Playstation 2, Playstation 3, Android Emulator box... Occasionally my laptop... Running against a port wall.
HDMI switches exist for a reason I guess.

My sound system is a Sony STR-DH770 7.2 channel A/V Receiver (https://www.sony.com/electronics/av-receivers/str-dh770), though I only do 7.1 (because I only have 1 sub-woofer and don't feel compelled to get a second one). I have the 7 speakers carefully arranged in the prescribed orientations throughout my office/game room, and I've calibrated their distances, etc. on the receiver.

The receiver itself is connected to my PC and all of my consoles that understand HDMI. I have both my PC and PS4 set to output in 7.1 and my PS3 and XB360 to output in 5.1 at all times (though my 360 has the 5.1 over HDMI bug, so sometimes there are false starts there). I also have my TV output to it via an optical cable so that streaming apps on my TV output in Dolby or DTS 5.1. The receiver does support Bluetooth as well, so my phone, tablet, and even my PC (if I don't want to turn on the TV) can stream music to it. While I'm usually a purist for how the audio signal is processed and relayed, I do generally default to the "Multi-Stereo" option on the receiver when I use Bluetooth because it really fills the room (I'm doing just that at this very moment).

The really nice thing is that my office is in the half-underground basement (i.e., when I look out the window, our yard is level with my torso), which means that I can have the sound system cranked and it barely carries throughout the house, let alone becomes a nuisance to our neighbors.

Have you considered some nice Virtual Surround headphones like others have mentioned? They were the only form of surround sound I had back when I lived in apartments (because like you and others on here, I don't want to force my noise -and, at the end of the day, it is largely just noise- onto my neighbors).

I just bought these for my brother for Christmas, and he seems to be extremely happy with them: https://steelseries.com/gaming-headsets/arctis-7

They seem to be compatible across quite a number of platforms and sometimes you can find them on sale (the manufacturer was actually selling them for $99.99 in late November).

A surround system sounds great at low volume as well. Most receivers, if not all, have settings for dynamic range, from full to standard to night mode. But indeed, if you like your sound loud, headphones will help you more often.

I have a HyperX Cloud Stinger headset for PC gaming and pretty bad TV speakers for console gaming. The TV speakers are even worse than the ones in the previous TV, but I've got used to it so it's not bad at all. I'd get better stuff but my apartment has much less room than I'd like to, so I'm unlikely to upgrade my TV audio equipment before moving to a new place (which ought to happen relatively soon but the exact timing is still unknown).

Yamaha YAS-108 Sound Bar

https://www.amazon.com/Yamaha-YAS-108-Built-Subwoofers-Bluetooth/dp/B07D73HMVR/ref=dp_ob_title_ce

I didn't want anything fancy and it's wayyyyy better than my TV's internal speakers (Sony X900f tv)