Welcome!

Here's my experiences over the past several years...

Tested multiple new bikes before lucking into my current Quick 1. Most of my testers were lower end bikes with larger tires (700x32 or 700x35). I found them to be more forgiving but not quite as lively and fast as the 700x30s on similar bikes.

My Quick 1 came with the original 700x30s and I put nearly 1500 miles on them before upgrading to 700x35c. The original Schwalbe Spicer KGuard tires were light and fast - it gave the bike a agile and sporty feel. I could keep up with the road bikes easier than I expected.

I then installed 700x35 Schwalbe Marathon GTs and they transformed the bike. It is much easier going on rough surfaces, I appreciate the improved ride due to decreased tire pressures, but notice it is not as nimble or quick. The Marathon GTs are VERY durable tires and have some mass to them and I'd rather deal with weight than a flat. If my memory serves me right, I run the Marathon GTs with 15 lbs less pressure than the Spicer KGuard.

I'm considering 700x32s as a compromise but have also considered going back 700x30s. Too much smaller and I think ride quality would decrease due to higher pressures. Friends that have moved up to 28's from the smaller sizes say that the 28's ride like a dream.

It seems to me the lesson learned is this: It is easier to move up in tire size than go down.