Looking to upgrade from my 6 yr old desktop PC to an iMac. Current hard drive is 1TB at 90% full, mostly photos. I'd like to get a 27" iMac, not sure that I require the 5K display. I use Photoshop/Lightroom for editing photos and a graphics program to run a digital cutter, along with docs and sheets, then the regular internet browsing and email checking. What specs would you recommend? Upgrade to 16gb memory? Am I better to get a 3TB fusion, or look to get a 1TB and an external HD? All flash storage is out of budget. And what seems like an after thought, preference on the magic mouse vs trackpad?