as you posted in the Pahoa forum, I'll comment on Lower Puna.
Yes, there are numerous rentals there that look very fun. I've never stayed in any of them, but if you find one you like and post the link and address I can tell you more about the location.
I like Alternative Hawaii.com as it attract the unusual. Also I'm a big fan of craigslist.org (Honolulu-Big Island), which is much used by folks here, and the old standard VRBO.
Here's the page for Puna vacation rentals from Alternative Hawaii:
I don't know of any waterfalls in Lower Puna, but you can get sunrise over the ocean.
For waterfall, have you looked at Emeraldview B&B in Hilo, which sits over the Wailuku River?
Special more spiritual places in lower Puna include Kehena, Kama'ili. Opihikao, Kapoho. Hawaiian Paradise Park's ocean area has some fine rentals. These are all newer homes and I wouldn't say the area feels so much like "real Hawaiian" although it's a very nice place to live. It's just not "seasoned" with time.
I personally wouldn't pick a place in Pahoa town, only because I'd rather be closer to the ocean. All the places near the coast also have Pahoa or Keaau mailing addresses because there is little mail delivery down there; find out the actual locations.
If I can help any further let me know!