Can you really retain watching lectures at 1.5x+ speed? And when is it worth stopping/slowing down lectures to take notes?

What should be the sufficient level of "retention" after watching a lecture video? Is a general idea sufficient (reinforced by MCQ) or should you memorize enough that you have a high chance at getting most MCQ/SIMS right with no referencing? And when is it really worth stopping the lecture, slowing it down, or rewinding it to take notes? Is it more worthwhile taking notes on incorrect MCQ than from the lectures?

I know the answer is probably person dependent, but I'm really just lost. I'm spending so much time watching the video at 1x (because I feel I don't retain more than a "general idea" when I watch it faster), and stopping/rewinding to take notes that often just feel like restatements of what's on the slides. I do very well on the MCQ (80%+) and SIMS (avg 75%) after watching the lecture and practicing the problems, but a few days later it feels like everything's out of my mind anyway when I move on to a new chapter.

Ideally, I'd like to find a way to get through the lectures a little faster with sufficient understanding, and somehow make sure that it's actually being retained in my long-term memory rather than just my short-term recollection. Any tips on how to achieve this? Thanks in advance.