Yep, Project X is one of the very smooth shoot 'em ups. It has many enemies on screen at the same time and is quite colorful. Would have been great to have more games based on that engine.
You are right about Rugff 'n Tumble and Wolfchild. Scrolling is not bad, but still it looks wrong to the eye. Maybe codetapper has a clue what's goning on in these games