Mac mini suitable for photo editing and heavy programs like photoshop lightroom etc.

Any M4 generation Mac mini will be fine as long as you configure it with sufficient RAM & storage. I suggest for your purposes 32GB RAM and 1TB SSD storage - that comes in at $1399. Beyond that it's only a matter of your budget & preferences. A similarly configured M4Pro comes in at $1999. IMHO there are better uses for that extra $600.

While the M4Pro has higher specs than the M4 it's significantly more expensive and you won't see much of a bump in performance if your target uses are Photoshop & Lightroom.

BTW, the only way your old 27" iMac could be used as a display for your mini is if you set up Screen Sharing on the mini and screen share from your iMac to the mini via your network. But you would still need a directly connected display/monitor/TV to set up the mini in the first place. And while Screen Sharing is a wonder, you probably won't be satisfied with it for photo editing.

I have a Mac Mini M4 Pro with 1 TB storage and 64 GB RAM. This one has 14 CPUs and 20 GPU cores. I use a 32-in LG 4K UltraFine display with a Belkin 8K High-Speed HDMI cable with it. That extra screen size is welcome over a 27-inch display, especially with multiple applications open.

First, you cannot any 5K iMac as a full video display with any Mac.

With that said, I personally would go for an MacMini Pro and a minimum of a 1 TB drive and as much RAM as you can possibly afford.

I say 512GB drive minimum because those apps can create very large caches, preview files, and databases that will consume lots of internal storage. This also assumes that you keep your photo libraries on an external drive and only keep work in progress files on the internal.

Through the years, for decent performance of Lightroom and Photoshop, I have found that 32 GB of RAM is a minimum for the combination of those apps to work well. As years go on, it only seems to be getting worse.

As a note, you need to make sure you get all of the above at time of purchase as the RAM and the drive are not user upgradable.

Finally, the reason for the Mini Pro is to get as much performance as you want. However, with the above suggestions, depending on the complexity of your work in Lightroom and Photoshop, you may be able to get by with just the M4 Mini and not the M4 Pro version.

Another consideration, once you add up all the options on a MacMini, you end up approaching or surpassing the new M4 MacStudio which has the M4 Max processor, faster bus speeds, faster internal SSD,etc.

A Mac mini with the M4 Pro should cover Lightroom and other heavier apps just fine.

If you pump it up to 48GB of RAM and a 1TB SSD, it still the same price as an entry level Mac Studio though which has less RAM and less storage.

Overall a Mac mini will be fine.

As to the 5K iMac, not it cannot be used as a display for the Mac mini or the Mac Studio. You'll need to get an actual display for either one.

Jasimoto81 wrote:

Also have an old iMac 27inch 5k which I would like to use as a screen.

You cannot use that iMac as a hardware monitor. Target Display Mode went away when the first 27" 5K Retina iMac came out in Late 2014, and never came back. (Apple also added restrictions so that no current Mac supports using any iMac as a Target Display.)

There is a product called Luna Display that could let you use the old iMac as a second display. As even the vendor acknowledges, the arrangement will not be as good as a connection to a real monitor.

Astropad – Use Your iMac as a Monitor: A Step-by-Step Guide [2025]

"Like any product, Luna Display does have limitations and it’s not recommended for high-motion content. For example, I wouldn’t recommend using Luna Display for gaming or video editing.

Since Luna Display is squeezing a 5K display through a USB cable, when lots of motion occurs on-screen (like from video playback or moving a window quickly) the screen can temporarily become pixelated before it renders in at full resolution."

You would still need to get at least one real hardware monitor for the Mac mini.

I've got an old (2019) 1.92TB Corsair Force MP510 connected externally in an NVMe enclosure to my 256GB Mac mini M4 as extra storage. It's about as fast as the internal SSD drive. See here...