Offense Defense Theme Team

Any advice on setting up a theme theme, choosing an offense and choosing a defense? I have mostly 96 and 97 players getting overrun by low 90s. I’m thinking the chemistry would really help, but I’m not sure where to begin. Is there a good post or video to get started on this?

Also still wondering if you spent 25,000 coins to change the players chemistry, is that refundable like abilities?

I’m not the best player just trying to have fun playing.

You do get refunded, however you only get 2,500 coins back for theme teams. If you're wanting to do a scheme team, you can't change the scheme of most cards. Ranked Rewards players and Honor Society are examples of ones you can change and that's free to do.

Is it better to focus on theme team or scheme team?

At this point probably a theme team since most cards are 96-97+ speed for skill positions. Try to fill with best available and then you can realistically switch between any scheme you want depending on the playbooks you want to run