Welcome back to the haunting hobby. I resisted for a long time to go with pneumatics, I like the motors because they don't require any air compressor... but I like the simplicity of the linear action of the cylinders. They can be tricky and a little dangerous when they do something unexpected -- this comes with experience and just be careful. Oh the other hand, the linkage situations get complicated and I'm not a mechanical engineer, but I studied the 4-bar linkage tutorials on-line and recommend getting some ideas of simple mechanisms work like sliders, rockers, cranks... while academic, it is foundational. Some of the haunt tutorials give good ideas, but they aren't always helpful. The best way is to experiment. I start with making a mock-up scaled model of my mechanism using stiff card stock and some small machine screws to figure out how the pivots, joints, actions, etc. will work. Also some trig is also good in calculating angular rotation and moving distances all as a starting point. Anyway, that's some food for thought. I'm sure others will chime in here and give you good advice. I think we're all learning here.
