"sweet spot" for 4* troops

Hello, I need some help.
I recently obtained several 4* troops and I want to level them. However I want to see which attributes (att, def, crit, etc) they obtain at different troop levels. However I have not been able to find a chart or any information regarding it online.

Does anyone know if something like this exists? If not, is there a “sweet spot” for 4 star levels, (best ROI) regarding their level?

Thanks in advance!