So does it make a big difference if your head coaching style is different from OC to QB coach and so on? On one of my teams I recently changed head coach. Before they were all pretty much same style.

only thing that matters is the coaching style of the head coach because what he runs on offense will be ran and same for defense

It will help you in the future if you want to promote a coordinator to head coach or a position coach to coordinator but the main thing is to get coaches on the rise. In case someone reading this doesn't know, coaches ratings rise and fall like players.

Do their ratings change throughout the season or is it once a year?

Idk, I only check coaches once a year, during Free Agency 1.

Jersey Generals...nice!
Trump would be proud, lol

I actually had Donald Trump as my punter when the league first started. I name my rookies.

https://usflwfl.myfootballnow.com/player/2029

Ratings can change throughout the season. They are neither as fluid as player ratings (low volatility) nor as precise (whole numbers). Unless one of your top three is already a bottom-of-the-barrel coach, you're unlikely to replace him for declining during the season. Checking in during early FA is usually enough.