If a print is really curly, say like Ilford Multigrade, I put it under weight, like art books, for days. I may even spritz them on the back with a bit of water to dampen them prior to that. If you weight them early on they usually flatten enough so that they behave under a matte. Adox and Bergger, the papers I'm using currently, seem less inclined to curl. The thinking regarding mattes v mounting, is, if a matte gets soiled or damaged, it can be easily replaced. Not if a mount suffers some damage. I think choosing a good paper, keeping wash temps reasonable and wet time short, and using whatever means you have to flatten your prints soon after processing should do the trick. Ages ago, there was a lab in NYC, I think it was called Scope, and they were custom B&W printers. Their prints were flat as a board. They did all of the above, and they said, they used Ilford Galleria, a graded paper. That's when a little light went on, and I realized some papers behave better that others.