[JrKASperov]

The practiced spellcaster feat does help, but not at all with your character. You see, practiced only gives a bonus of max +4 to your spellcaster level if it is lower than your character level. But in your case, your spellcaster level equals your character level ( character = 20 vs. spellcaster = 10 (wizard) + 10 (red wiz) ).

This feat works brilliantly, for example, for eldritch knights if they decide to take 2 fighter levels. They then lose out on 1 spellcaster level from eldritch knight first level, and 2 from fighter levels. Now practiced spellcaster ups your spellcaster level by three, making sure your fireball still does damage as if you were a full wizard.