On the motion capture front, to convey Venom’s movements, Tom Hardy doesn’t have the height or the build, so that too was eschewed.
The fact that Tom Hardy didn’t perform motion capture for Venom would seem to indicate that the digital animators created all of the character’s movements and expressions.
It sounds like practical and logistical considerations ruled out the use of motion capture more than anything else.
That is unless they really did recruit a really tall person for the movements.