Downloading iPhone photos to computer with Photos application

Do you have "My Photo Stream" enabled in both your Mac and iPhone:

If you do on both devices any photo taken on your iPhone will automatically be imported into the Mac's Photos library when they are both connected to the same LAN.

What happens when you click on "import all new ..." (top right), or when you select an item(s) and then click on import?

If you use iCloud to sync, your photos will download automatically to your laptop as well as any connected devices.

Of course. You can either import images directly when connected. Or, enable iCloud Photos on all devices for automatic transfer.

Correct. If you sync with iCloud, everything will be kept in sync. So, edits on one device will reflect on all connected devices.