I think that the center of the watcher looks like a monitor... I think it's forerunner because: Monitor looking center + Sentinel body shape + the name watcher i'm guessing describes the sentinel's purpose (similarly to the sentinel enforcer).
Some thoughts on the crawler: It's anatomy seems strange as its name and posture suggest it runs on all four but somethings suggest it not being on all 4 such as no tail, I think the arms and leg lengths seem odd, and the most odd thing is that the arms can bend forward (think about this one can a dog, zebra, etc bend their arms in two directions...). Also, it's muscles suggest it probably isn't mechanical and it doesn't seem like any flood. I'm pretty excited to see what this one turns out to be if it's real!
