1. I have chosen the L5 because it is perfect for my workflow. I carry it every day from my home into the musicstudio and back. I have monitors at both places, so sticking it into my backpack is no effort at all. It's really small but it doesn't try to be the smallest which is good because you have enough space for aircooling of powerful CPUs. Especially in my case as I don't use a dedicated GPU.
2. I still would choose the small version. Sooner or later I will need a powerful graphics card for 3d realtime visualisation. But that would be something in the range of rtx2080. As soon as there is a intel mini-itx MOBO with full range TB3 I will add an eGPU case to the L5. That way I can decide if I can leave the eGPU at home or not.
... but that just me, very niche I guess :-)
Sounds like you might be a good candidate for an APU version of the L5! I don't need anything more than a GT 1030 myself (allows me to have anti-aliased visuals using CAD software), so I sometimes think a smaller model might be nice, but I hate to limit my choices when Mini-ITX boards have a PCIe slot.