I have extensive experience with the lapability of the 2-in-1 form factor, as I own and extensively used the Surface 3, and briefly owned and used the Surface 4 Pro, and own and extensively now use the Lenovo Miix 700.
Seriously, many hours at this.
I find that the form factor containing the kickstand in the same manner as Surface and Lenovo Miix – and the Eve – is surprisingly very lapable for a couple of reasons:
With the kickstand being able to be adjusted to most any angle, you can adjust it so that its held by digging (gently) into your leg.
With the keyboards covers being softer and more flexible, you can either keep it straight or angle it into any direction which is good for making adjustments.
It’s a toss-up really whether a full shell laptop or the 2-in-1 with kickstand is better on the lap because while the laptop is a more rigid structure, it heats up much quicker and you don’t get as much flexibility in the keyboard that you do in your lap with the keyboard cover.
Also, I think the kickstand is actually better than having a more rigid flat underneath surface for lapability because it’s less likely to slide off your lap because it’s got the resistance of the kickstand edges that slow down any sliding.
Just my two cents.