Please support me grow to a full BlenderArtist

I am experienced at gmax, but since it is a dead-end software, I’ve moved to Blender.
So far, I’ve worked through “N00b to Pro” up to 5.3 (Rendering) , tried several tutorials linked from and I am moving to my own projects. At this moment, I can
Model at mediocore quality
Do basic texturing and lighting
Do beginner-level animation
So, my first project is a box-y fusion-thrust engine, with ion accelerators.
And I fear I need some support here already… Is it possible to apply subsurf just one mesh? Or to use subsurf function on something and not to the other, they have to be separate objects? I want to subsurf just the line of torus inside.

hi 2chan & welome blender artists … yes they have to be seperate objects and while in editing mode press p for seperating objects .

Thanks! Your advice was put in practice, and I’m getting something out.
Progress update:
In people’s experience, what’s the best way to get a glowing plasma gas effect? It would be cool to have plasma exhaust blasting out of those magnetic nozzles.
Use halo in materials? Use particles? Which one is better?