Here's my take
TWF should be a theme anyone can take, balanced by the fact that it allows more consistent damage AND some extra AC, whereas THF should have higher DPR but no AC bonus. So, like +2 AC if you are dual-wielding swords + you get a second attack but only 1/2 str bonus (or even none) on each for damage. Higher level feats or theme benefits could increase the str bonus on each, from 0 to 1/2 to full str mod on each swing.
When you get other bonuses and magic weapons and so on, you may see high DPR, such as combining it with some rogue levels and advantage (presuming advantage is not that easy to come by).
I like a big two-handed sword to be the ultimate damage, while two weapons are very offensive but also have some defensive benefit, and sword and board is least offensive but the shield benefit, needs to be higher than +2 for a heavy shield. And it should definitely benefit Dex saves too, IMO, as per 4e. Or maybe a S+B theme would allow a shield bash attack and boost the shield bonus, or grant interrupt-like block moves that would count as an action against your next turn's action. Definitely better to block that dragon's talon or duck for cover from his Breath weapon now than be a charred, pulpy stain on the floor next to his other victims.
Just an at-will tank guy with his shield blocking interrupt move, could ostensibly just plough his way through really tough enemy blows ala Captain America and wait for the right moment to retaliate. I.e. Being defensive so your friends can be offensive. Probably a good thing to have a counter move to do a free sword thrust against any enemy who runs away from you, even if you've already used your defensive shield move for the round.
Slowing you down by 5 feet is a good idea too. So the big slow hulking tank CAN drop his shield to TRY to jump over the chasm there. Leave it to magic shields to provide full benefit with no slow-down.