So I decided to mark this as an answer because there doesn't seem to be a way for the user to improve things when watching Twitch in a browser.

After further research, I found for myself that it's more feasible to look for other methods to mitigate Twitch's poor performance overall.
Here is the alternative method which makes it possible to watch a video stream in VLC.
I found this guide on xmodulo.com, initially via linux.com:

FIRST THINGS FIRST

• You can paste into the terminal via Ctrl + Shift + V. This should make life a bit easier for you, when you just want to start it up real quick. No need to type it out or use the mouse.




• Twitch supports timecodes! You can start a video at the 4th minute by adding ?t=4m at the end of the URL.

Livestreamer is a command line interface (CLI) client which, upon given a streaming URL, retrieves live streaming video from the URL, and pipes it into a native video player running on local host. So with Livestreamer, you can enjoy live streaming from various sources via a much stable and lightweight video player such as VLC or mplayer, without opening a web browser. Currently, Livestreamer supports streaming from over 20 different web sites including Dailymotion, YouTube Live, Twitch/Justin.tv, Livestream and UStream.

Install Livestreamer on Ubuntu

$ sudo apt-get install python-pip

$ sudo pip install livestreamer 

By default, Livestreamer attempts to pipe streaming video into VLC player. Thus you also need to install VLC player on your Linux system:

$ sudo apt-get install vlc

Watch Live Streaming from the Command Line with Livestreamer

To watch any live streaming channel/program, first obtain its corresponding URL from its official site.

For example, let's say the URL for the live streaming content that you want to watch is http://www.youtube.com/watch?v=Vw4KVoEVcr.

To check available streaming quality (i.e., bitrate) of the given content, simply run livestreamer command with the URL:

$ livestreamer http://www.youtube.com/watch?v=Vw4KVoEVcr0

The output for that is

[cli][info] Found matching plugin youtube for URL http://www.youtube.com/watch?v=Vw4KVoEVcr0

Available streams: 144p (worst), 240p, 360p (best)

To watch a live stream in the best available quality, run livestreamer command in the following format. This will automatically launch VLC player, and streaming will start on VLC:

$ livestreamer http://www.youtube.com/watch?v=U4Pw3ofFWgs best 

To watch a live stream in specific streaming quality (e.g., 360p), run livestreamer as follows:

$ livestreamer http://www.youtube.com/watch?v=U4Pw3ofFWgs 360p

If you have your own favorite streaming player, you can let Livestreamer launch the player instead of default VLC, as follows:

$ livestreamer --player=mplayer http://www.youtube.com/watch?v=U4Pw3ofFWgs 360