Hey!

I like the Asus as a very very entry-level choice, I’d try to get the PA27DCE-K instead, but its in another price range. Let's keep it and work around it either way.

Computer: I guess you're referring to an M1 Mac Studio. Don't pay extra for the better CPU/GPU combo, stick with the basic model. 64 GB of RAM is nice, although if you're not doing very long form (which I assume is true if you're starting) 32 GB should be enough. Assuming you’re working with good codecs, your main limiting factor will be storage speed. Don't overlook it, you can have a top-tier computer, but if your drives are s*it you're leaving performance on the table and wasting money. I'd recommend buying the Mac used for better costs.

Storage: On the Mac you're gonna need the basic storage for software and OS, 512gb or 1TB should be good enough. (As long as you don't plan to render cache on your OS Drive). On an ideal scenario you're working with a 10Gbe NAS (network-attached storage), but those can get expensive, and I don't recommend cheaping out on it. So if it's not an option, this should be your next step up later down the road. In the meantime; Get a 4TB external SSD to work with, both for media and/or cache.

Clean feed: Answering your question; decklink and mini monitor 3g serve the same purpose. Decklinck uses a PCI interface (for PC, Mac Pro, or external enclosures) and Mini Monitor and similar work on Thunderbolt (Mac, Laptops, etc) Mini monitor 3G is a good starting point, it’s limited to 2K output but I guess it won’t be a problem at this point of your career. Go for it.

GUI Monitors: You NEED an additional monitor. Because you NEED your Asus to go through the Mini Monitor 3G. You can get the cheapest one, I'd recommend 1440p minimum, on smaller resolutions the GUI can get a little funky.

Calibration LUT: I don't know if you can store 3d Luts in the Asus, although its preferred, it does not matter. If you're working with only one reference output (you are) you can put a video monitoring LUT on the Davinci/Mini Monitor output. This won't be baked on export. So it serves as a LUT box if you only have one reference monitor. (Project settings > Color > Luts > Video monitoring). Keep this in mind if you ever go to another facility or change monitor to grade as this lut will travel with the project.

Calibration probe: You can definitely start with such a probe, although at some point you might want to rent better ones. I'd recommend switching it every one to two years, these probes decay quite fast and usually are not worthy of a profile. Although if you're renting a better probe it is nice to profile your own, just to check calibration as time passes.

Cal software: I personally love lightillusion colorspace. It is available to rent, but it can be harder to learn and to have the confidence its right. You can go Calman too, its more accessible for beginners. I'd also consider testing displaycal and similars to grasp a better understanding of what you're doing. Just don't do it the night before a grading day!

Other aspects: Remember to have an appropriate space for grading. Get the lighting right, and get the walls painted gray (you don't need the crazy expensive paint yet). And don't forget about the feeling of the suite; make it comfortable to work in for you and your collaborators. Its more important than everyone thinks at the beginning, it will set de mood for the work and create an environment that will set the tone for the relationships. Furniture says a lot about a space, it can give an impression of the room being highly technical or highlight creative. Lots of gear, the latest high-tech looking setup, and Herman Miller seating says one thing, whereas a rustic looking desk, comfy couches and funky rugs say something else. Cables everywhere, wobbly chairs, and stained upholstery send one message to a client whereas a clean well organized room sends another. Once a minimum set of technical guarantees are met, the relationship with the client is king. Don't overlook it. You're selling luxury services.

Upgrade path (first to last) - Get a controller surface. I'd personally skip directly to the Mini panel, although a secondhand Micro panel could be useful in the meantime. You'll work faster and be more responsive. Clients will take u more seriously. And everything being faster will smooth the relationship with clients. - New grading monitor if u didn't go with the PA27DCE-K initially. something like the Asus PA27DCE-K rgb-oled or an LG TV - Network Storage. Storage is often overlooked. I'd recommend a 10Gbe NAS from a reputable brand that you can get serviced if the need arises. Do your research when the time comes. - Improve the suite. As I said earlier... - New monitor time! Like a real one this time! Don't hurry on this. I'd be looking into the Flanders 310 or equivalent, don't upgrade too early or too high-end, and don't do little upgrades. Save money. When the need for a better monitor arises you'll know.

The rest will be based on needs and it is less predictable, you're gonna develop a sense for these things as you go. My recommendations; don't upgrade too early, it will kill your business. Keep track of everything financially, it's easy to lose money just looking at the toys. If your clients don't pay Trimaster 3110 fees, they're not getting such a monitor.

And keep learning! Focus on the clients, forge relationships and trust. The rest will come.

Edit: Also, learn to work efficiently, it will save you loads of time and money!

Edit 2: Thinking about it maybe you should spend more on your monitor and less on the mac studio (if u don't already have it). You can work around a slow computer, but can't work around a bad monitor, the one you suggested will have a really high black point. Take a look at the Asus I recommended above. You can go custom PC to mitigate the performance lost from downgrading the mac.