This may not be exactly what you’re looking for but have you considered using Firefox containers, automatically logging in to a different Google account for each container? I’m fairly sure this would work on mobile (probably only Android though), and is almost certainly more convenient and polished than a separate YouTube client.
Out of curiosity, are you using WiFi, and what frequency?
A little while ago I had an issue where my controller would interfere with my 2.4GHz WiFi and make my computer basically unusable for online games. This isn’t really the same situation but I imagine something similar could happen in reverse.
Otherwise I’ve never had any issues with controller latency though. It’s weird that it’s so significant for you.