definitely get that Ryan Hall arm triangles set if you can
I'll try and get you a few free resources. Braulio Estima probably has the best arm triangles of any modern grappler ever. Watch his matches and I would subscribe for a month of his website just to watch all of his arm triangles in sparring. A search for arm triangle turns up 252 of them in his sparring sessions.
https://tinyurl.com/y8d88juy And he finishes them basically the same as Ryan Hall and co.
Braulio is great to study because there aren't a ton of grapplers that consistently get the classic kata gatame/side choke style arm triangle when they are not strikes involved. In pure grappling (either points or sub-only) most high level grapplers don't expose themselves in that way for that sub.
Most of the exposure I see for it in pure grappling comes from leg drag passing or being on someone's back and they start getting their back to the mat, and then finally from full mount (Gordon Ryan v Craig Jones at ADCC is a recent example.)
From top side control or top neon belly I just don't see many bottom player's exposing their elbows in that way and not a lot of top players good enough at kata gatame to expose it forcefully.