Question 2:
If you think any particular title/thumbnail combo is more enticing, or see a different possibility I could do let me know!
Yeah I think a few are better than others. Remember, titles and thumbnails require a specific GOAL. and that goal is ALWAYS "something, something, curiosity, something" aka, it doesn't really matter what it is but it does matter that your viewer gets imensely curious reading your titles and seeing your thumbnails. "Keywords" aren't worth your time or attention. Trust me. I chased the SEO alogirtum for so long until I realized that only works if you want search results (and most people DO NOT search for new "entertainment" videos to watch over searching for a specific topic, usually to learn something, and then clicking off). It's best to stick to catching their eyes and attention in their homepage and scroll feed.
With this in mind:
"I spent 6 months scamming Twitch's most Annoying Users" is too long, not as inticing, and doesn't potray the actual video clearly in a concise manner.
"How I Scammed the biggest Scammers on Twitch" is much better, clearer, and more curisoity driven. The question here would likely be "how?" or maybe depending on thumbnail "who did he scam?" and "how did they react?"
"How I scammed Twitch's most obnoxious scammers" is the same as the last one, but implies some sort of justice focus and potentially a more drastic reaction (we associate obnoxious people as having more reactive-qualities, like being whiny, egotisitcal, dramatic, etc, which you're implying a bit more here at the cost of read time)
I'd say after all that, you can combine the last two to get a new title:
"Scamming obnoxious scammers on Twitch."
Or if you want to venture out a bit more, I have a couple more