The most common complications from jaw angle implants are asymmetry and not achieving the desired look. The implants are placed under the masseter muscles and have no effect on facial expressive movements. There will be some temporary stiffness in opening your mouth but that goes away within a few weeks.
Mandibular angle implants could be made of different materials
silicone is probably the best one to use because it's easy to remove if the need be
implants are placed under periosteum so they should not affect muscles of facial expression and lips
The use of angle implants is very common to some of us; and the main risk is infection. The area of the bottom jaw is prone to infection more than eg the chin; and if you get an infection, you must usually remove the implants, let it heal and, if you wish/ replace it. Since there is a reduced likelihood of 'two' implants getting infected on both the right and left, the decision to remove 'only one' is something to think about.