I'm using OpenDNS (since Google's DNS prefers European IPs over Asian/Singaporean IPs) and I just ran a test with Among Us - and no buffering.
Here's a screenshot of the stream details:
https://pasteboard.co/JIp2F3q.png
And here's the ping to live.twitch.tv
paping v1.5.5 - Copyright (c) 2011 Mike Lovell
Connecting to bkk.contribute.live-video.net [99.181.88.30] on TCP 443:
Connected to 99.181.88.30: time=133.86ms protocol=TCP port=443
Connected to 99.181.88.30: time=138.04ms protocol=TCP port=443
Connected to 99.181.88.30: time=136.53ms protocol=TCP port=443
Connected to 99.181.88.30: time=133.73ms protocol=TCP port=443
Connection statistics:
Attempted = 4, Connected = 4, Failed = 0 (0.00%)
Approximate connection times:
Minimum = 133.73ms, Maximum = 138.04ms, Average = 135.54ms
But interestingly, the stream seems to be fetching data from the London datacenter (video-edge-c67a80.lhr03.abs.hls.ttvnw.net) so changing the DNS won't really have an impact as Twitch is probably assigning these datacenters (just as Youtube assigns them to your ISP's cache).
Anyway, I'm on GPON as well.