I’m a photographer as a hobby. Could I get the 512GB M3 iMac and just use external hard drive sticks (or cases) for my storage for my photos I take or do I need to get a 1TB internal hard drive? I would like to get a computer this week but it’s delayed if I get it with a 1TB hard drive. I’m forced to get the 512GB model if I want my computer soon over the holidays. What should I do?? I can get it with 16GB of memory in time.
Yes, you can use external storage. But it is very inconvenient to use external on a notebook computer that you carry around with you. If this is for a desktop, like a Mini or a Mac Studio then the external drive works well.
An external SSD can be very fast. The best ones are almost as fast as the Mac's internal SSD.
The other option is to store photos on a network-attached device and then keep the photos you are currently working on in the internal drive. The network connection is not very fast but you'd only use it now and then to move entire folders of files.
Also, in either case, you will need a backup system. The first one should be Apple's Time Machine and for that the drive must be external. But you can use a big, slow, and low-cost mechanical spinning disk. Buy one that is 2x or 3x as large as all of the data you will have some years from now. A 4TB drive would work
Then in addition to Time Machine, you need some kind of off-site backup, a cloud service works well.
16GM of RAM works well for photo editing.
Summary. Technically it works but no one likes using external storage with a notebook. You will end up copying files to and from the external drive and leaving it at home. But external drives work well for desktop computers.