Check with your print provider first - they should have templates or provide you with one.
For an Accordian fold each panel should be the same size.
Each panel folds neatly onto each other.

For a tri-fold brochure the pages fold into each other - called a ROLL FOLD. You see the "outer flap" - if that was the same size as the page that it is folding onto - the "inner left" page would not be able to fold over the top of it. That's because the outer flap would be sitting right on the crease of the inner flap.
Most printers and finishers know this - and typically will trim off an extra 1mm anyway to account for this.

The Fold Factory https://www.foldfactory.com/ have very good folds and a Plugin for InDesign
https://www.foldfactory.com/pages/template-builder to allow you to create a template - however, I would recommend learning how to do this yourself, it's very easy.
There are also free online resources if you search for them - I found this one
InDesign Brochure Templates for Design and Layout for Printing
But back to the original point - contact your print provider who will set you up with a template that suits their capabilities.