I use the sql database :)
It is great but as you said a bit costly. Not much of an expert of the topic of indexing, but if it improves the data searching and retrieving that is great! Maybe we should look to implement this in some future hardfork, since jsons are now so wildly used and probably will grow even bigger.

The NFT options is something interesting, I was just exposed to NFTs with gerbers test game .... wasn't aware that you can do an unlimited objects with them. Looks like the NFT will open yet another door on the Steem blockchain.