An overview is a general argument at the top of your speech, usually introduced in rebuttal and extended in summary and final focus. This argument is something that the judge will be focusing on, that's particularly important for the round. Think carefully about what you're including in an overview, as if the overview is worth reading at all, it will likely be at the top of your next few speeches. (If the overview isn't the most important thing in the round, why are you reading it at the beginning of your speech? Read something else that the judge absolutely must focus on instead.) There are three basic overviews, each of which is a way for the judge to approach the round. If the overview is emphasized sufficiently, your side of the debate should be approached through this overview, so make it round-winning.
A defensive overview is a crucial response to their entire case. Since this response likely exposes a flaw in their case as a whole, this overview can easily be extended in each following speech. There are a few advantages to this overview. First, running responses more often makes you better at defending and extending them, making your argumentation more concise and coherent. Second, you save time by making a response that applies to multiple arguments, and you also focus the judges on this idea that makes it so your opponents can't win. All overviews here are just ways you can consolidate argumentation with similar benefits.
An example can be seen in the video, in Sandeep's rebuttal (first aff, around 14:10). He first establishes how the argument he's responding to relates to both their contentions, then makes his response. And as expected, when Danny responds to Ardrey Kell's case around 29:33, the first argument extended is the overview, and when Sandeep responds around 37:41, the first argument is the overview again. Remembering this response is easy, helping with lay judges; the overview saves frees up time for other arguments, helping with flow judges. Strategically grouping the arguments your opponents make lets you go more in-depth on the responses you make, meaning you can go more in-depth with warranting, evidence, and examples, to ensure your side takes out their case.
Bonus points if your defensive overview relates to the narrative of your argument! A defensive argument made in the second round by the negative is that since Mexico was gradually liberalizing pre-NAFTA, the amount of trade today would've been the same. While not read as an overview in rebuttal, after the second rebuttal MSJ sees that it's going to be crucial to the argument, and extends it at the top of their remaining speeches.
An impact overview is an argument about which impacts should be prioritized in the round (which is probably going to be whatever your impact is). To help with the clarity of this overview, you should contextualize your impact at the top. Some ideas for this are examples of when your impact happens, strong statistics or numbers, or elaborations of the specific warrants in your impact. Remember, having a weighing overview doesn't mean that's the only place you can weigh, as link weighing can often be integrated in responses against your opponent's case, more specific to individual warrants.
Impact comparison must go farther than the classic buzzwords of magnitude, probability, and timeframe. The idea that "if we both win our arguments, we stop 1 million deaths but they only stop 500,000" is the extent of your analysis is usually insufficient - nobody just thinks we should save fewer lives. Instead, either focus on the differences between the mechanisms you introduce, as seen in the first example, or elaborate on the specific differences between your arguments and why they're voting issues. "But I did weigh!" does not apply when your analysis is insufficient to distinguish voting issues. Be nuanced!
In the first example, Sandeep does comparison between the weighing mechanisms introduced around 38:33 in his final focus, explaining reasons why one is more important than the other. When in your own rounds or when looking back on old ones, notice situations when both sides have basic weighing introduced in the round. Weighing is supposed to resolve situations where both sides have offensive arguments, but when both sides have basic weighing, the problem arises again until one side does weighing on a higher level.
In the second example, Daniel does impact weighing at the beginning of his rebuttal at 11:38, giving multiple reasons to prioritize the US recession caused by debt reduction over the developing country recessions. This is nuanced - too many times teams read a specific link chain to their impact, then weigh the idea of "war!" or "recession!" in general. Not only does Daniel's style of weighing re-emphasize his internal links, but it's much harder to answer since it's actually specific to Poly's arguments.
Uniqueness is generally analysis of what is happening in the status quo. The general idea of a uniqueness overview is analysis of the direction or situation of the status quo, thus strengthening one side's argument. The ideas of uniqueness are pretty similar from topic to topic, you can read more about it here.
The advantage of the uniqueness overview is the way it frames the entire case. While your opponent may have multiple arguments or links, if they're contingent on one scenario, a uniqueness argument can function as both terminal defense and offense for your side.
In the video, Chad begins the uniqueness debate with an overview around 12:04, arguing both that tensions in the South China Sea are escalating and that the advocacy advanced by the negative (hard power) has failed to stop this escalation. This overview establishes that the status quo is trending towards the agreed-upon impact. This means the neg's argument is partially non-unique and the aff risks solving it.
Devesh responds around 16:23, giving three responses. The general function of the responses is to point out that the status quo is good and will not trend towards a terminal conflict, and that instead negating decreases the risk of conflict. This responds to the most dangerous part of the overview, that the neg's arguments are potentially nonunique and a reason to affirm, and instead gives a good reason to negate. If the status quo has no risk of an impact, then the only side who disrupts it will risk a negative impact.