It would appear that you sent the same message several times, so I'll only reply to this one.
The ENGINE feature implies other features, such as ROTATION. If you compile in ROTATIONAL_INERTIA but do not set it, ESPResSo will use the default values. Choosing a different value will modify the physics, but if you don't specify it, it will be as though you did not activate the feature. Obviously, everything that can rotate in MD has rotational inertia.
Also, please be mindful that high values of the swimming velocity (force) need to be paired with appropriately chosen friction coefficients and length of the time step, to be in the regime where the integrator is stable and produces the right physics.