Cables are cheap, especially if you just buy a box of cable and terminate it yourself, and can be run temporarily. You can look into Powerline adapters, but they're significantly more expensive and while better than wifi, aren't as good as a dedicated Cat5e cable.
Yes, some people leave the Twitch Dashboard 'preview' open though, or a browser window of their own stream to check the quality. Which would cause problems.
2000kbps is still the most you want to go for, but wifi is very prone to interference, along with being a shared bandwidth space. Meaning everyone on the same channel, even on separate networks, shares the same maximum throughput. So if your neighbor is on the same channel and starts transferring a large file, YOUR throughput on your network will tank. Also, if you have anything that puts out EMF on the same band it can easily interfere with data transfer.
It's not meant to replace network cabling, but to complement it for devices you carry around with you for lightweight use where dragging a cable with you while you move around the house/office would be unfeasible. Any permanent or semi-permanent/regular-usage location should have a cable run to it.