Challenge 1: Choppy Timeline Playback on Underpowered Hardware — Solution Walkthrough

The feature that solves this:

Proxies.

How this addresses the described problem:

Per this chapter's own material, a proxy is a lower-resolution,
easier-to-decode stand-in file generated automatically from the
original footage, used only during editing. Generating proxies for
the high-resolution footage means the timeline plays back the much
lighter proxy files while editing, which the computer can decode and
display smoothly, even though it struggled with the original
full-resolution footage directly.

Whether this affects the final exported video's quality:

No. Per this chapter's own warning box, Resolve automatically relinks
to the original, full-resolution footage at export time (Chapter 8's
own Deliver page), regardless of what resolution was used to edit
smoothly during the actual editing process. The proxy exists purely
as a working convenience and is never present in the final rendered
output — the exported video uses the original, full-quality footage
throughout.

WHY THIS WORKS AS AN ANSWER
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This exercise is a direct, practical application of this chapter's own
proxy material to the exact symptom (choppy playback on underpowered
hardware) proxies are specifically built to solve, correctly
confirming that final export quality is unaffected.