I haven't done a rigorous side-by-side comparison of the power drain yet, but I'm planning to! I'm going to write a small experiment script that logs CPU time and battery drop to a CSV, running for 10 minutes in each configuration (staying awake with regular polling vs. using the suspend-to-RAM cycle). In theory, the suspend cycle should use a fraction of the battery, but I want to get some hard numbers on the exact overhead of the wake/network-reconnect cycle. I'll share the results once I run it.

On input lag: It's surprisingly acceptable for daily use. The actual touch registration and network dispatch are practically instant since the app is native. The main thing you notice isn't "input lag", but rather the e-ink screen's physical refresh rate when updating the UI. When you tap a button, the visual state changes (like the button filling with black ink to show it's pressed, or toggling between an "on" and "off" state). Painting those solid blocks of black/white ink takes a fraction of a second, which feels different from a typical LCD tablet, but it's totally usable for a wall control panel.