the Elcan has always peaked my interest but I've never had the opportunity to handle one let alone shoot with one. how forgiving is the eyebox vs a good LVPO and vs. a T2?
1x eyebox is good, a bit better than your gold standard 1-6 LPVOs like the Razor and K16i. It is noticeably larger when moving from right to left (or up and down) but, presumably due to the design of the prism, is funnily enough about the same when moving from left to right.
4x eyebox is excellent, it barely shrinks from 1x. I would venture it might be somewhere around 1.5-2x better than your average high dollar LPVO on the same magnification setting.
No scope will be as forgiving as a T2, Elcan included.
does the eye relief shift when moving between 1x & 4x?
No. However it does become somewhat less forgiving of eye relief error, meaning that if you were off to begin with, you will see more obscuration if you switch to 4x.
how usable is the reticle when not illuminated?
Eh, it's ok. Probably a bit better than the NX8 and ATACR I would imagine but not as good as the full crosshair designs like the Razor Gen 2. Certainly much more usable than something like the Razor Gen 3 or the S&B 1-8 Dual CC I would think, though I frankly prefer to use illumination on any scope for anything besides precision bench shooting if at all possible.
is it daylight bright @ 1x?
Yes and also at 4x, the illumination isn't supposed to change between magnification settings. The 5th and highest setting is what I would call nuclear bright, as in, not only will it not wash out but it will glow brilliantly even against bright light backgrounds.
Note that I'm referring to the dot illumination here, the full reticle illumination will only be low light visible. It is very useful for night ranging though.