Having closely examined many of the Cobb OTS maps, I can tell you right now that in terms of actual fuel and timing tables it is going to be as safe or safer than most custom tunes. Cobb barely touches the rich fuel AFR targets. On most maps they're basically stock, which means plenty rich provided that you followed the instructions and used a catted exhaust and stock intake. The timing isn't that aggressive but fuel quality can vary some so if you're really worried a custom tune can retard the timing in a few areas to make it safer.
The MAF scaling will be fine if you are using the stock intake as the instructions require. The wastegate duty cycle requirements will vary a little bit because everybody is at a different altitude or is using a somewhat different exhaust.
A lot of custom tunes are going to run some combination of more boost, more timing, and less/leaner fuel. All those decrease safety margin to some extent, but they create more power over the OTS maps. An OTS map could be safer if there were some outstanding issue that needed to be fixed with the in the first place, like you ignored the instructions and ran a catless exhaust.
Bottom line: OTS map on the proper fuel, with catted exhaust and stock intake, will usually push the engine less than a custom tune designed to extract more power.