Re. 2., absolutely. They are different. Part of what is provided by TXHASH+CSFS is provided by TxhashKey, and it may be more likely to reach consensus due to not adding other uses of hashes for which all technical objections may not have been addressed. I admit that I’m not well versed in the objections to CSFS, but I’m confident that the technical objections to TxhashKey can be addressed.
Re. 3., I definitely understand your hesitation around pre-defined modes (we can see the challenges with such in my own objections to APO/APOAS). That said, I struggle to see the downside to providing some best effort pre-defined modes along with the complete flag set.