A flash drive is not necessary to put songs on an iPhone. I'd venture to say that's the hard way because iPhones have a proprietary port (Lightning).
Should be able to plug the phone into your computer and let it sync.
If you want a bad### camera, get a 14 Pro (or Pro Max), be ready to spend $1000, more if you want extra storage. IMO, 256GB is a minimum since storage is not expandable. You may be able to catch deals on the 13 Pro (or Pro Max) since it's last years model. I'm continued to be impressed with my 13 Pro Max camera.
If you don't care so much about the premier device, look at the 14 or 14 plus or the 13. They have great cameras, just not the premier camera. There's nothing wrong with the 12 either.
The budget minded option is no doubt the iPhone SE, however, it has the smallest screen size of all the options. It's based on the iPhone 8, but has modern chips.
If you're looking to pay cash, look at
Apple's refurbished section where you can get an iPhone 11, 11 Pro, 11 Pro Max, 12, 12 Pro or 12 Pro Max. It's not a spectacular deal, but it's a deal in the Apple world.