Apologies for dumb question but we play skirmish so we may be mixing things up.

In skirmish, Fenn can "Assault."

Also, can allies (e.g., Rebel Troopers) attack twice? We say "no."

Thanks in advance. We are trying out the app and haven't played campaign normally.

Any other big differences that we may be missing?

In campaign, all heroes (the ones that comes with big sheets like Fenn, Diala) can do it. All non-hero (the ones that use a single card, like Rebel Troopers) may not

In skirmish there's no "hero", everyone is a non-hero. Skirmish version of Fenn just overrides that restriction

All heroes (big sheets, not the playing card size cards) also come with the two following intrinsic abilities:

Take 1 strain to gain 1 movement point during their activation, up to twice per activation,without spending an action.

Spend 1 surge during attack to recover 1 strain.

9 minutes ago, Tvboy said:

All heroes (big sheets, not the playing card size cards) also come with the two following intrinsic abilities:

Take 1 strain to gain 1 movement point during their activation, up to twice per activation,without spending an action.

Spend 1 surge during attack to recover 1 strain.

Also: when a hero recovers strain, for every strain not recovered, recover damage instead. (This ability is removed in the LotA app.)