I didn't tack Mickey when I neutered him, it's a much more invasive procedure than just the neuter. I feed RAW, and based on dane owner's experience this can drastically reduce the chances of bloat. Actually, I have not yet found a dane owner who's had a RAW dog bloat.
I also don't restrict their behavior before or after eating, to me this would add to their stress which IMO is much more dangerous.
In the case of an unknown history, I would seriously consider tacking, but I wouldn't stress too much if I couldn't afford it or felt it was too risky. Dogs can still die even if tacked, and there's no guarantee that the tack will hold.