Hi,
I would ride on the bike lanes at first in order to see what it's like and observe how motorized traffic is like in Espoo. I have cycled in capital area just for one day and I felt like the bike lanes are okay'ish for velomobile too. You might need to reverse at some crossings though in case your velomobile has 13m turning radius or close to that.
I'm pretty sure there are some sections where riding among cars 40-50 km/h might be smoother, it's just that there's always the risk that someone does not see you and reverses, switches lane or passes the car behind you and crashes to your side.
Past that point accident I am not sure how well local traffic regulations and laws protect a cyclist who rides in a (low) position that makes it even easier to end up into car driver's dead angle of vision, especially if there's a bike lane right next to the point of accident. In Finland law states that we have to use a bike lane if there is one, but there are some exceptions to that rule. Generally police's opinion is "Bikes on the bike lane. Period."