My go to back in The Day was just Ubuntu because I was lazy.

So we have a bias towards Debian-based distros.

it’s not been playing nice with my Zen 4 desktop when it comes to ACPI power states (no sleep, doesn’t reliably turn the power off when i ask it to turn off, etc).

However, a newer kernel is definitely preferred.

is also something based on a normal distro that most people write guides for because I am a smoothbrain.

And finally, healthy access to documentation.

Based on the above, I would not pick:

• Debian Stable or any distro based on it. They ship with the 6.1 kernel, which launched only a couple months (January 2023) after the launch of Zen 4 (September 2022). I’m aware that access to newer kernels is possible. However, at that point, why even bother with Debian Stable to begin with?
• While both of Debian’s Testing and Sid/Unstable branches have access to newer kernels from the get-go, distros that ship the latest kernel by default (e.g. Arch, Fedora, openSUSE Tumbleweed and their derivatives) are simply better for offering an end-user product.
• Arch, Fedora, openSUSE Tumbleweed and their derivatives are primarily dismissed for not being based on Debian. Though, the fact that they’re more towards the rolling release side of things does play a minor role as well. By their very nature, they will change. Hence it’s less ideal for “set-and-forget” setups.
• Pop_OS!’ team seems to be primarily focused on delivering their upcoming COSMIC DE. For this reason, the distro has been in relative limbo. Therefore, I can’t recommend it.
• TUXEDO OS is dismissed for being relatively unpopular. Lots of other Debian(/Ubuntu) derivatives are dismissed for various reasons.

Let’s get to the actual recommendation, Linux Mint seems to be tailor-made for your use case:

• Based on Ubuntu, but without Snaps. While you can choose to use Linux Mint Debian Edition (LMDE) instead, that one doesn’t come with the latest kernel. So the recommendation is for (standard/vanilla) Linux Mint.
• Their forums are full with up-to-date and (relatively) well-written guides; while the excellent ArchWiki is arguably better, Linux Mint isn’t a slouch either. Furthermore, as Linux Mint is very popular, you can simply expect to find solutions to most things that might come up.

should I be looking at any other distros?

From what I can tell,

• containerization is appealing to you; almost all of them employ this to some degree, but some more than others. More on that later.
• your preference goes out to (closer to) stock experiences rather than opinionated ones

I take it that you’d rather stick to the (relatively-speaking) more popular options. Not that popularity is necessarily good, rather not used by anyone else is bad.

Then, the following are worth looking at as well:

• NixOS; it’s quite different to all the others, perhaps we may call it obtuse by comparison. But, it has been going at it for the longest; heck, it’s older than Ubuntu. And, in my humble opinion, is one of the main inspirations for the others. But, contrary to the likes of Fedora Atomic or Vanilla OS, it doesn’t go all-in on OCI. Therefore, it might not be as smooth of a transition.
• Guix System; the answer to “What if we had FSF-compliant NixOS, but with actually good documentation?” Jokes aside, this is a cool and underrated distro.
• openSUSE Aeon; relatively new still, but perhaps already offers the most secure OOTB experience. However, from what I can tell, in terms of transition to OCI, it doesn’t strive to be very revolutionary (as of yet). Fedora Atomic seems to be a relatively significant (and IMO exciting) departure from traditional Fedora. By contrast, openSUSE Aeon seems more like a _revolution with a (very) small r. Though, one may argue this is mostly due to maturity. Consider openSUSE Kalpa if you’re feeling particularly adventurous.
• uBlue’s base images; Aurora, Bazzite and Bluefin are built from these. These are vanilla images with only hardware enablement, codecs, other RPM Fusion goodies and more that anyone installing Fedora Atomic would want on their systems anyways.
• Create your own; See this link if you know how to write containerfiles. See this link if you prefer yaml (.yml to be more precise) instead. The previous links were more focused on Fedora Atomic, this link offers Vanilla OS’ answer.

Other distros found on lists like this one didn’t make the cut for various reasons; sometimes it’s just because I haven’t heard enough of it.

Do I need to shift my expectations of an immutable distro even more?

Uhmm…, I don’t know exactly what your expectations are 😜.

FWIW, from what I gather, either (something based on) Fedora Atomic or Vanilla OS should be right up your alley.