Experience knows best. Getting close to replacing a clutch ( bike sat for years so it's on my list ) .
1- What clutch components are recommended for a CT3. Brand, etc.
2- Do I need the rubber rings
3- Can I clean the metal rings and reuse
4- Is it wise to replace the springs even if they look fine
 

Can't advise on brand as the ones I've used in all my CTs were from Yambits in the UK.
You can discard the rubber rings.
Yes, you can re-use the metal rings so long as they are flat.
You can re-use the springs as long as the length is in spec (free length 31.5mm -1mm tolerance).

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I usually find the clutch springs have sagged a bit on inspection .
As they are relatively cheap , I just replace them as a matter of course .
I'd rather spend a little more money up front , than have to go back and do the job again .