The mono screen is a non-issue. It's a reasonable resolution and has excellent daylight visibility.
..so how does it perform after dark? I assume there is a LCD backlight?
I've been a etrex hcx user for many years but I fear their age is coming to a close and I'm not particularly enthused by the modern Garmin offerings. The option (AIUI) to do on the fly route planning on a phone app and use that to programme the bolt is particularly attractive... I ve had enough of squinting at 2" screens....
As mentioned above, yes there's a backlight. The only slight annoyance is that there's no "do nothing, turn backlight on" button. This quirk is shared with the Garmin Edges but not the eTrex.
I would keep your expectations low about the on-the-fly route planning, although there's no technical reason why it couldn't work a good deal better than it currently does, and Wahoo have been pretty good about providing firmware updates that improve the product.