4GB RX 470/480, or either GTX 1060. 980, I believe is a little over the top for that need. However, the 3GB 1060 may see some issues sooner than the other options due to its VRAM amount, plus it isn't actually a GTX 1060.
On reference? That shouldn't be possible. Aftermarket ones tend to run in the 70-83 area under load. I believe reference is around high 80's and throttles at 90 or so. All the temps are safe, it's just about what you're OK with in temps and sound.
The reference card. I know that many of the RX cards can be undervolted to help with temperatures, but the heatsink used on the reference is not nearly as large as the aftermarket ones. So, no matter what, the reference or the Sapphire Platinum will be hotter. Your best bet is finding someone who has the reference style RX 470.
I use two sets at work. Neither have broken yet and they're mostly OK with me. My work is in a lab, so nothing extreme.
MPOW
These I like more than the others. They fit and sound better.
Aukey
And these are not so great with my ears. Plus have a thinner sound.
For the RX cards, most people tend toward the MSI Gaming X, Sapphire Nitro+, or the XFX GTR. If any of those are in your price range, go for it. And there is no Founder's Edition. That's some silly term used to charge more.
Is it possible that the speakers run on USB instead of a traditional audio controller and that the USB controller just isn't good? Because I thought I had heard that this MBP has issues running some USB devices concurrently.
A TV will be 60Hz, yes. Its those higher refresh rates like 120 that are fake. The main problem with a TV is getting it to cooperate with a computer and the input lag that TV's inherently have. If it has a game mode, that helps.
I have the corsair fans which I have on my H80i. The included ones were way too loud. For me, they're quiet up to 80%. But I use a splitter and at that they're reported to be spinning at 1100RPM. So, there could very well be better options.