Baldur's Gate : The Sword Coast Chronicles : NWN2 Persistent World

Do these feats offer anything beyond the dc increase?

Spellfocus Conjuration
All summons can be further improved (to a max limit of 24 HD) by:
Conjuration focus grants +1 HD.
Greater Conjuration focus grants a total of +2 HD.
Epic Conjuration focus grants a total of +4 HD.
Red Wizard Spec: Conjuration grants +1 HD.

Polymorph Focus
Similiar to conjuration and necromancy, Transmutation focus will grant boni to polymorph and shapechange.
Transmutation focus grants +1 AC to polymorph and shapechange forms.
Greater Transmutation focus grants a total of +2 AC to polymorph and shapechange forms.
Epic Transmutation focus grants a total of +4 AC to polymorph and shapechange forms.
Red Wizard Spec: Transmutation grants +1 AC to polymorph and shapechange forms.

..........

Are those the only ones?

I think SF Necromancy does the same for animated/created undead. SF Transmutation improves your shapechange stats, I think. There are people with more experience in that than me and I hope they can add their 2 cents.

Below gives the details regarding Transmutation, Conjuration and Necromancy changes.

Polymorph and Shapechange overhaul

Conjuration and Necromancy changes