Well, like I said, I don't actually KNOW any of these places, and I can only go by what little I can see online about them including any reviews or referrals I can find. I certainly always SAY, "Talk to them first". That way you can certainly get a feel for what they know or if it feels like they are not knowledgeable.
Honestly, as USAFRet mentioned, stopping by Microcenter is probably a good idea, unless that's where you already went and are talking about. Certainly THEY should know what an NVME drive is.
As for the place in Niles, I don't think I ever heard back from them so IDK on that one.
Also, a few other resources. If you haven't committed to anything yet.
These guys are not local to you, but might be worth talking to about doing this FOR you as they are probably THE most trustworthy and respected company online that does EXACTLY what you are looking for. I can't speak to them being able to work with hardware you get, but it is at least a reputable resource that has MUCH experience with very high end systems.
Puget Systems specializes in tailor-made computing solutions for all business needs. We build quality workstations and servers for your unique workflows.
www.pugetsystems.com
In Chicago, these are some further resources worth TALKING TO.
These guys have six stores in Chicago. That, to me, says something at least. Doesn't mean they have experience in the kind of build you want, but talk to them, see what they say. You'll be able to tell if they are monkeys or actually know their stuff. Anybody who says "What's that?" is probably not the right place. Anybody who doesn't seem like they are fluent, probably isn't.
Chicago Computer Club is your complete computer store! We offer computer sales both new & refurbished, computer repair & upgrades and technical support
www.cccc.us
This is the one in Niles. I don't know if they do what you need done but I suspect they CAN. Again, talking to them in person is probably the best way to get a feel for whether they are the right people or not. If not, one of these places might be able to at least TELL you who they'd recommend. Then, go TALK to that place or person.
These days most good systems builders are independent, but there are still some good builders out there working out of standard mom and pop repair shops. Some larger facilities are notable systems builders and IT specialists that have simply grown because they are successful and good at what they do, but, some place don't really customize. They offer cookie cutter turn key systems and that is what they are knowledgeable in. Ask about the latest tech or special hardware and they go all goofy eyed and their tongues swell up.
Now offering curbside drop-off & pick-up at our Niles location! We're all using our computers now more than ever - whether it's keeping in touch with loved ones, completing creative projects, or...
www.mnsystems.com
In the end, Microcenter STILL might end up being your best best and will almost certainly be the best prices for anything they stock or can get.
If you lived in my state, I'd offer to built it for you for a very reasonable price, but unfortunately you are pretty far away from me as I'm in Colorado.