Orbi AC3000 RBK50 router with wall plug-ins

I recently purchased the Orbi AC3000 that has one router and two wall plug-ins. I live in a 2800sf two story house in the mountains and have had problems with wifi and cell phone coverage for many years. I'm not the only one suffering in my area and when I ask others what they've done to remedy the problem most of the positive replies said they're using the Orbi.  So I'm trying the Orbi. It's been about 2 months now and I still have problems with the wifi cutting out, but not as much, and I still have problems getting a signal in one part of the house even though I have a wall plug-in in the next room (the second wall plug-in is upstairs). I'm wondering if maybe I need something stronger - maybe the 2 wall plug-ins are too weak and I need to use 2 or 3 of the larger ones that sit on a shelf.  So my question is, should I use the equipment that I currently have - One rounter with the two wall plug-ins or should I switch to using either 2 or 3 of the Orbi RBK50's? Is 3 overkill? Does it matter if it has Daisy Chain or do they all have it now with the update?  Thank you for your input