I'm pretty sure you can land district court clerkships in places like n. dakota, louisiana, georgia, etc. by being top 5% at regional TTTs.
Um, no. No no no. Three times more no.
From a "TTT," you need to be top five in the class -- minimum -- for an AIII clerkship. Probably more like top three. Look at the numbers. You have lower top 50 schools and second tier schools placing like 2-3 grads a year in AIII clerkships. Once you get to the real third tier schools, it's basically the valedictorian or salutatorian, and maybe the next guy if they both pass at the local district court.
The class of schools where top 5% makes you competitive for an AIII clerkship are those just outside of the T14, like in the 15-25 range.
As for the the relative difficulty of clerking vs. biglaw out of a TTT, I think this depends on the TTT and home market. At the (non-NYC) V20 firm I was at, the local TTT schools usually placed a person or two at my firm in every class. If the other big firms hired even half that many, that's a lot more biglaw associates (between 5% and 10% of the class) than AIII clerks (maybe 3 or 4) in the class.
People reeeeeaaallly don't know how competitive AIII clerkships are these days, especially out of the T14 (and really T6, and really really HSY). You have people from (say) Michigan with top 15% grades with LR applying broadly and not getting an interview.