1. Yes, give RT RAID a try and see how it works out for you.
Even though some users have trouble with it, it is actually stable for most (those that follow its usage rules). It is all about usage pattern.
2. The only gotcha with Snapshot RAID is explained here: http://wiki.flexraid.com/2011/10/18/understanding-the-limitations-of-snapshot-raid/
Writing new data to the array is safe. Even deleting data is safe if you enable the Snapshot RAID recycle bin feature.
Only edits are an issue and I doubt that you will be editing 17TB of data.
Most people will tend to separate the data that will rarely be edited and protect it through Snapshot RAID.
You will find that this will be the bulk of your data.
For the remainder of the data (usually a small set), either mirror it or go with RT RAID if that set is large enough to warrant it.
For instance, if you determine that the data you constantly change is under 2TB, then mirroring is the best approach for that data.