Yes, that's what I am thinking as well. Will I need to upgrade the memory too? As for updating the bios after installing it, is that on the web site for the mobo?
Yes the bios update is on their website, you would need to install that before you put the CPU in otherwise the PC won't boot. I believe this was your board:
https://www.asrock.com/mb/amd/b450 steel legend/#BIOS
You'd know more about photo editing software than me so I couldn't comment on how much RAM you might need to get optimal performance for your workload. If your concerned about RAM speed then it tends to have rather minor impacts on CPU performance unless your running in single channel mode.
Dual channel is especially important for iGPU's because they are quite bandwidth hungry. If you have 2 sticks of DDR4 something though then I wouldn't worry.