After watching the latest episode, I'm thinking a few things:
1) Wanda has been "pushed" to do everything she is doing to have a perfect life & avoid the reality of her situation (dead Vision, looked at as a criminal, etc). I think that Wanda knows exactly who it is that's pushing her & that person showed her how to really use her powers.
2) I think she, being pushed, stole the Vision & went to Westview to recreate the Vision using her regular powers. Doing this under all that stress & grief pushed her powers to the point of warping reality around her in a hexagonal shape that surrounded the town (the "hex" that Darcy speaks on). Previously, her mindwarps was only effective locally.
3) I think we have misunderstood Wanda's powers all this time. She isn't just a high powered telekinetic/telepath, she's also a reality warper (yes, I know that's what she is in the comic but it was never referenced in the movies). Notice that when she "mindwarps", the warps seems to be in a hexagonal shape. In Age of Ultron, all of the "mindwarps" were in areas the shape of a hexagon. Thor's party, Black Widow's ballerina room, Cap's ballroom, all hexagonal shapes. Also note that they were also premonitions of MCU events...MCU events that the Avengers lost....or better yet, one of MANY futures....kinda like what Dr. Strange saw when he viewed all of those realities...
4) Finally, I think Wanda just expanded her hex power in that last episode. Notice after she "enhanced" the hex (turning it reddish), Darcy comments on Sony movie Quicksilver showing up by saying "She recast Pietro?". Why would she say that? Because Wanda extended the field to include the SWORD base as part of the Wandavision show. That way, she controls them as well. Her mindwarps work on anything in her field.
5) Agnes is someone that can resist Wanda's power, but is playing along for some reason. I think that Agnes isn't the villain. I do think she is the one that pushed Wanda to this point & didn't realize exactly what she actually has done until now. The fact that the children are "real" & having the knowledge that Wanda can "create life" was the trigger that made Agnes realize that Wanda has gone too far. I think that Wanda is the villain & has always been the villain of this show. I think that Wanda's power is destabilizing other realities & causing chaos outside of the hex area. That's why Mysterio was around to stop those creatures from other realities & why the next Dr. Strange movie is going to deal with this...because Wanda probably let Dormammu or some other mystic threat in unwittingly.