Im not so sure. In terms of the cosmos, I think the engineers are fairly closeby e.g. same galaxy. The fact that they have hypersleep pods doesnt suggest they have unlocked the secrets to rapid or instantaneous intergalactic travel speeds and also points to their mortality and ability to age.
I would expect that since earthlings were their creations, that engineers roam within a certain radius to check on progress and observe their creations/experiments.
The homeworld could be dozens of stars away from lv426, but I couldnt imagine they are thousands of star distances away, also taking into account the human crew lifetimes of the covenant and whatever speeds they travel at.
Astrophysicists think other solar systems also have kuiper belts and oort clouds and planet-9 equivalents, so theres a lot of variety just in a single solar system.