Difference between In form and On form

in form—

1. in structure:

• Cretan buildings are simple in form, conforming to architectural norms of Byzantine provenance.

2. in good physical or mental condition:

• Even if a horse is in form a bad trip almost surely will cancel its chances.

3. as a mere formality:

• The laws, which heretofore existed only in form, have been thoroughly enforced.

on form—

1. on the basis of previous results:

• On form, they have no chance of winning today.

2. = in form 2:

• We all knew that Michael was always on form when he played and he exceeded his own expectations today!