Please, if you find it possible, ask concrete questions. You may choose to start by reading the data/care sheets on this fish from the many good places, like Planetcatfish, Seriouslyfish, Scotcat, LiveAquaria, FishBase, Catalog of Fishes, etc. Another great resource is performing a search on MFK Catfish forum.
No, they are not like TSN. TSN are normally quite a bit more predatory while acharas/marbled Pim/Leiarius marmoratus are mostly scavengers that will hunt only if there is no other food source whatsoever. They are more interactive than a TSN and easier to hand-feed. While TSN in captivity would grow to 3' or more, a marbled pim usually don't exceed 2.5'. In the wild, most TSNs (it is a genus, not one species) max out at 4'-5', while marbled pims do not exceed 3'.
As a partially sight-oriented predator, TSNs may be a bit more active, cruising around in day light, especially in sub-adult/young adult years. In comparison, marbled pims prefer to hide and are more nocturnal. But when big, the latter would swim around too, still I think less so than a TSN.