Can anyone recommend the best Stand / Dock / Memory Storage unit for the Mac Mini M4 and M4 Pro?

On stands-with-SSD docks for the new minis, the big split is USB-C/USB4 (10–40 Gbps) “hub-stands” vs true TB5 devices (rare in this form factor). Both the Minisopuru iExpandMate MINI4PRO and UGREEN’s Mac mini stand are USB-C (not Thunderbolt) add-ons with an internal NVMe bay and a display port hanging off that same 10 Gbps link.

That means: HDMI is capped at 4K60, and the NVMe tops out around ~800–1,000 MB/s in the real world—fine for libraries and Time Machine, not scratch for 8K RAW.

Based on what I found on the Internet, the Minisopuru explicitly advertises a 4K60 HDMI output and SD at ~104 MB/s (UHS-I). UGREEN’s spec sheet focuses on more/faster front ports (three 10 Gbps USB-A, two 10 Gbps USB-C) and SD listed at ~170 MB/s, but their HDMI variant is inconsistent—some UGREEN bundles are DP-only, so watch the exact SKU.

What you didn't provide in your post is what are your monitor resolutions/refresh targets and what you plan to park in the NVMe bay.

The Mac mini M4 Pro actually gives you full Thunderbolt 4 on its USB-C ports—so you already have the benefit of Thunderbolt, including compatibility with Thunderbolt 5 devices when they arrive. The docks on the market often advertise USB-C front ports at slower speeds, but the main passthrough port to your Mac stays Thunderbolt. For your dual-monitor 1080p setup and planned 4 TB SSD backup drive, a dock like the Minisopuru or UGREEN option will serve you well while still freeing a Thunderbolt port for expansion.

Here’s what I’d suggest that you consider and which dock edges out in which respects:

• You want two ASUS monitors at 1920×1080, 60Hz. Neither dock is overkill for that. So display-wise, both will satisfy you easily. The UGREEN might give more flexibility if you ever change monitors or want higher refresh rates.
• You want to free up a Thunderbolt port. Both docks help with that, by giving you an HDMI or DisplayPort out of the dock so you don’t have to use as many of the Mac Mini’s built-in ports.
• You want backup storage with an NVMe SSD, speed isn’t critical but some speed helps. The 10 Gbps UGREEN models probably offer slightly better throughput than the Minisopuru for data transfer, especially for large files. But if you’ll mostly use it for backup and casual usage, the difference may not be very noticeable.

With that said, I’d lean towards the UGREEN 10-Gbps dock variant unless looks/design are more important than raw speed, because it gives you more future headroom (more high-speed ports, more display flexibility). But if you prefer the cleaner integrated look and know that your usage will stay modest (1080p, backups, light work), the Minisopuru will serve you very well and probably give you fewer “what ifs” down the road.

For what it's worth, I ended up getting just a basic stand with no hub. The stand keeps it off my desk and hopefully minimizes vacuuming up dust and cat hair. I didn't want to put something under the computer that might generate heat and put pressure on the mini cooling system. Sure, I find the number of ports somewhat limiting. For my external drives, a wired mouse and keyboard, and an optical drive, I was able to make use out of my old 10 port, powered USB-2 hub. It's a mini so I am not about to need to walk around the house with it and I have my display on a stand and the port is under the stand and doesn't take up any more desktop real-estate. You may say USB-2 is slow, but it's plenty for what I use it for. My backup utilities are automatic so so what it they take a few minutes longer to do the job?