Great progression and it sounds like you're landing in a great spot. I think you'll like the GX a lot. I'm a former 3rd gen 4Runner nut too and those things with the TRD supercharger are an absolute blast.
Welcome to the forum and post some pics when she arrives!
The Eibach Pro Truck is a good kit but IMO is not the goldilocks for on-road driving. It's good quality but definitely has less refined damping characteristics than something like the Dobinsons Twin Tube Kit. If I were chasing the best possible on-road ride quality with a mild lift, I would go...
You bet!
Like @nonamex said, I wouldn't drive on it long-term but if you're only using it for emergencies, I wouldn't sweat it.
If you did do all 5, I'd recommend then using a 5-tire rotation so you actually get utility out of it!
If you're happy with the 265's then there's no real advantage to the 275's. I like them because they are a little more substantial which looks good and fills out the fenders a little more, but that's it. Hope this helps!
Good digressive valving operates essentially as you've observed, but the actual feel and personality of the kit can vary a LOT. For example Bilstein and OME are both digressive but have completely different and unique personalities.
Digressive does not mean stiff, but rather it cheats a bit by...
In a vacuum, progressive springs ride better than linear springs. But in my experience, damping philosophy has a greater impact on ride quality than spring rates alone. DJ's Sled provided an excellent writeup on his experience going from stock to OME MT64 and his take is spot on with what I've...
I've never run and OME kit that didn't blow me away. I'm a suspension snob and it's actually concerning how few kits get it right out of the box. OME kits just deliver every time. Glad to see you're loving your MT64s!