"In my search I keep coming back to the Thinkpad T460p wondering if the bulky plastic case is worth the tradeoff for the raw power. It's maddening I can't have both."
That's the thing. It's a trade off. If Apple could make a laptop with >16GB RAM AND a sleek design AND good battery life, they would do that. But they can't.
The limitation is actually 16GB of of LPDDR3.
Intel Skylake CPUs support up to 128GB of unbuffered DDR4, depending upon chipset, and don't support LPDDR4 at all at present.
Apple chose to use the older, lower-power RAM specification and thus adopted the limitation. If they'd left the battery capacity unchanged then perhaps they could have used DDR4 but apparently their priority was reduced overall volume.
I don't understand the obsession with laptops. They have shit keyboards, small screens, are far more fragile, have less room to work (don't like having to clown-car my arms to type/use a touchpad), are generally under powered yet still exceedingly expensive. Yea, I have one at home and 2 at work - but I also have an illicit desktop at work (actually not allowed... for no reason).
The laptop's ONLY advantage is in portability, imo. But then I've never sat in a noisy coffee shop or whatever on one. I don't see the appeal in that either - I make my own coffee (roast/grind/boiled filtered water/french press) which is better quality for less money. To each their own I guess.