Is an obj printable? That's a solid maybe with a few asterisks attached.
obj files are arguably better for defining an object that you want printed but if your slicer (Cura, Slic3r, PrusaSlicer, etc.) doesn't understand what you're feeding it then you're in for a headache. Most slicers currently do have support for obj files but again, that doesn't guarantee that it's usable for 3D printing. For an object to be printable it needs to be manifold (no holes, no intersecting faces, no zero thickness surfaces, plenty of other possible errors) for a slicer to create a layer by layer set of instructions to be converted to gcode for the machine. To be more user friendly some slicers have included an automatic repair tool for common issues in files but if the problem is too great such as the whole object being zero wall thickness it'll either make an interesting approximation or just outright fail at producing a set of gcode instructions.
So really, is an obj printable?
-Yes if your slicer supports the format.
-Yes if the model is well defined.