I think you're right on... a large tarp and no bivy vs. a small tarp and a bivy are pretty much 2 great options. I don't think you could go wrong with either.
A couple months ago, I started using a tarp exclusively and went with a solo-sized tarp and bivy combo. I believe this is going to offer me a handful of options in the long run:
Cool night with no precip: ditch the tarp
Light precip with no heavy winds: ditch the bivy
Heavy precip with directional rain coming at you: use both
I'm in Maryland too, so I know about our humid summers and how gross it can get. For this, you could bring the tarp and a bug bivy or MLD Serenity Shelter. You'll have the bug protection and great airflow.
I did a hike with some guys last weekend, and I had an MLD solo tarp and TiGoat bivy and another guy had an 8'x10' ID sil tarp. He pitched his tarp to the ground on the sides and it was palatial! Even if it had poured all night, he would have stayed dry. But, he did experience some condensation under that big old tarp.
I've taken my solo tarp and bivy into downpours and had no issues with condensation (even in warmer showers) or rain getting in the bivy. The highly water resistant and highly breathable fabric of my bivy (TiGoat uses Intrepid, which, as I understand it, is just a rip stop version of Momentum) kept all of it at bay.
I think if you went with a larger tarp without a bivy, a flat tarp (i.e. an 8x10 tarp) would be the way to go. Lots of pitching options to keep weather at bay. But, Maryland's (and the surrounding areas) mosquitoes in the summer are pretty nasty. I would want the bug protection.
But, again, I don't think you can go wrong with either option. Tarp camping is awesome, and I love the simplicity, the views and the connection to the place around me. Don't think I'll ever go back to a full on tent.
Best of luck!