1) This is just bit of inconvenient UI as far as I can tell. The only way to see what's queued is in the list of units in the army, the icon will get a +n indicating the number of units queued for it.
2) No idea, but I've definitely seen odd behavior with the queuing, I can never quite tell what's happening there.
This whole feature is a bit disappointing. The updates for instant arrival are great in theory, but I've never found it evenly slightly usable to supply an army this way, the UI is just too much of a pain vs repeat queues and waypoints on my factories. And even if you do use it, armies can be full? I hadn't even noticed previously, although it now explains some of the weird behavior in trying to form armies with many units.
Point being, armies being full and disabling the build menu makes it rather difficult to use recruitment to produce units at the same scale as factories, teleportation or not.
Also, it seems a bit silly that the teleportation benefit would only apply if you use one UI menu vs the other. How about if the factory waypoint is on an army, that works too? (assuming it doesn't now, not sure I've tries of if you even can set an army on a waypoint)