It was the updated icons that required the most adjustment, so I thought I would cover that. My current system is to separate my messages by "unread" and "everything else" so that may look different to you in the screen shot below.
You'll notice that the icons that usually sit at the top are gone. They appear, as seen below, when you click on a message.
Here are the icons on their own. Maybe you're an Old Person who does well with symbols. Or maybe you're like me. (My overall tip is to hover your mouse over an icon you don't know and wait for a description to appear.)
The icon on the far left is the SELECT icon. You might use this to SELECT ALL messages.
The next icon is a folder with an arrow on it. This ARCHIVES your messages (to ALL MAIL; it will keep any labels you have applied). The third from left icon is a STOP SIGN. This reports a selected message as spam. The TRASH CAN sends messages to the trash.
I hope "mark as read" is explanatory.
Here's the MOVE TO in action. This is what you see when you click the arrow. You then move the message to the option provided.
And here are the LABELS.