I agree with all those who have said the transition can take time. I do 2/3 of my runs barefoot and the others in standard VFF. I would do them all barefoot but the paths I run on are rough and spiky and the time off helps recovery.
The VFF are superb for me, you have to adjust your style obviously but i have found it lessens impacts. You can feel the ground beneath your foot but barely more than in a pair of spongies. The separate toes is to encourage the foot to spread and distribute your weight more evenly.
I am not a lightweight either, 108Kg, so they should be fine for everyone. If you get excessive calf pain it could be that you are too far up on your toes, I have tried to land on my forefoot marginally before allowing the rest of the mid-foot and heel to touchdown. I know when I’m knackered and losing form as I will occasionally clunk my heels.
Matt