Well, stealth is never a requirement. You can absolutely stomp around the entire game shouting and banging the walls. You'll have to fight more, and occasionally in less ideal situations, if you're never sneaky at all. But you can absolutely just murderhobo through the game.
If you do want to do stealth, there are a few things to consider. Some stuff has true sight, or machine sight - cameras, robots, and maybe one or two other special things, too. This true/machine sight means that your stealth is useless. You have to keep your distance so they don't notice you, or keep using LOS breaks like corridor turns. Hiding in vents and behind closed doors is good juju, too. Sometimes, you'll need to take out a mechanical enemy really quickly (notice how low the health is on those cameras?) then run to a good out-of-the-way place and hide until all the enemies come check out the poor exploded camera than get bored and go back to their patrols/loiter locations. Then you can sneak by the living enemies.
High Agility will help but is not necessary for stealthy play. The Interloper feat is very helpful but not necessary for stealthy play. Tailoring and Electronics will help a lot, but they're not necessary. What is necessary is a careful play style that understands that you're going to need to strike from the shadows and just maybe retreat right on back again, possibly several times in a row in some of the busier maps.
And of course, you can always just armor up and say forget about it, then shoot everyone in the face. Ta-da! Role playing!
