There are two main forks of BSD. One is considered more secure than Linux. The other is considered extremely secure. I've not played with BSD in a number of years and have no opinion on TrueOS. I can tell you for sure that if you want integrity, you're looking at some form of BSD. As a side note, I know there exists some level of linix binary compatibility on BSD. I've never played with it and I don't know the full implications of it. But at least you have application options should you desire.