"Facebook Container" seems redundant if you already use Multi-Account Containers and set it up accordingly, yes. Other than that it doesn't sound over-the top at all and a reasonable configuration.

Doesn’t Strict mode block third-party cookies anyway?

Almost, but not entirely. For that you need First-party Isolation (privacy.firstparty.isolate pref: https://bugzilla.mozilla.org/show_bug.cgi?id=1330467),

containerises first-party cookies too, but I wouldn’t need that.

It does do that - if it didn't, there wouldn't be any "multi-account" to it.

With a profile like that you might also find Konform Browser relevant to your interests with more private defaults and convenient toggling of modes and features. https://konform-browser.codeberg.page/

It comes with a debloated version of Multi-Account Containers, which can also be installed as a normal addon into other Firefox builds: https://codeberg.org/konsortium/multi-account-containers-lite