Caves don't interest me, since there are no shipwrecks in caves, so I really cannot help you with your cave issue.
As to my view of the comparative equipment risks associated with SCRs compared with O/C, I have not read anything in the media about SCR failures. Whether that makes them safe or not I cannot say.
Regarding CCRs, it seems fairly clear to anyone who is honest about the issue that CCRs have the highest risk of scuba equipment malfunction.
Regarding O/C, it seems fairly clear as well that this is the safest and most reliable form of scuba. O/C also has the highest limitations on depth and bottom time however, which are the most obvious drawbacks. But safety and reliability are not drawbacks of O/C.
CCRs have lots of cheerleaders, but that does not change reality. One by one, they get to individually face reality, ultimately.