As far as defense goes, in a perfect world one person would be big and clear the crease, the other would be small+speedy and would be relied on for pursuit and outlet passes.
Small and speedy is extremely useful on defense for being first on puck, but you need a partner who is going to support, and you need support in your own end because it's so easy to get creamed when you have the puck. I'm not even talking about playing like an Erik Karlsson meme and jumping into the play or leading the rush. In the ozone, the extra speed can allow you to be first on puck along the boards and get it back into the forwards who are hopefully deep. In the neutral and d-zone, you can beat basically everybody else to any stray pucks and get it to somebody else. The problem is, it all falls apart if there is no support.
Being big is useful, because almost all goals are scored in or around the slot. So being able to effectively clear the slot and front of net makes it a lot harder to score. The downside of being big and using a dfd or enforcer d type is that passing is much harder and forwards in drop in almost never support when you regain the puck in your own zone, they sprint up the ice. You also are super slow, so pursuit in the d-zone is useless, and you can't really apply any pressure in the o-zone or else you'll be caught flat footed and get beat. That's why if you're big, it's better to have a d-partner who can be the small/speedy and pursue.
It's very difficult to play builds that are any end of the extreme in drop in, because if you don't get a d-partner who is willing or able to compensate for the very exaggerated short comings of those builds, you get massively handicapped.