I went on a similar search and settled on the Osprey Arcane tote: https://www.osprey.com/us/en/product/osprey-arcane-tote-pack-ARCANTOTPKS20.html

It comes in a lot of color options - both professional and fun. So much so that it was really hard for me to pick just one color! It has tote straps and separate padded backpack straps. Both can be stowed in pockets. The backpack straps connect via little carabiners on the back. They can be a little fiddly - I looked at two colors and it was much harder to get the straps clipped in on one color than on the other - but I figured if they drove me crazy enough I'd just attach a couple of these to them to make it easier. It has a 16" padded laptop sleeve, a large sleeve in front for papers, a zippered pocket, a big outside zippered pocket, and an outside stuff area. Pretty clean and simple. There is a logo at the bottom and on the backpack strap, but it's pretty clean.