Yes, thinning paints and applying a wash produces pretty good results for beginners and from there it’s easy to add other techniques that are within your own capabilities.

This is the way.

(Except those are the worst options for Tabaxi, ranger and Rouges are best)

Because of the stat bonuses? Just take the Monsters of the Multiverse version where you can choose the bonuses freely (everything else is the same).

Personally, I would not try to play dnd “optimally”, it takes away from the creativity and produces either bland or disjointed characters.