I would say 30L is definitely on larger end of what most folks would think is an EDC. Personally, I think a big part of what is too big is how big it looks on you. A 30L bag on some who is 5'1 and 100lbs is very different then on someone that is 6'3 and 230lbs. I've used the TB Synik 30L as an EDC without any concerns.
Can you take a 30L backpack on a plane?
The Travel Backpack is our most ergonomic, most organized, and most adjustable backpack. The 40L will max out carry on dimensions on most airlines so you never have to check a bag. For stricter airlines, like RyanAir, 30L will be a better choice.
Is 30L enough for a weekend trip?
Here are some approximate guidelines to give you a sense of luggage and duffel sizes (by volume in liters) and how much they can accommodate: 30-50 liters: In general, luggage that has a capacity of about 50 liters or less is sufficient for a weekend trip.