When you played the Thief games, did you use multiple saves?

Hiding bodies is simpler than you might expect. As long as they're in a location where Garrett would be invisible (completely darkened Light Gem), they're invisible unless they're touched.

One of the earliest things to learn is that guards in Thief games are bliiiind as heeeellll. Or perhaps Garrett just has a more finely tuned visual acuity than they do.

But they have really great ears and they can detect when footsteps are yours versus when they're the footsteps of other guards lol.