First off: don't ever expect shop clerks at Best Buy, Target or any place like that to know shit about computers in the first place and even less about any specialized field involving computers.
These people work for a commission. Bob will work in the computers aisle today but tomorrow he's likely to be in the dishwashers area. Bob will generally have a generic pitch for a type or
another of apparatus and sprinkle it with the tidbits he'll have read here and there to make himself look competent in the eyes of any punter who'll wash out at his doorstep. His team manager
will have assembled all the minions in the morning to tell them that this and that item must fly off the shelves because you don't want outdated shit to remain too long in stocks. So, whoever
gets a customer to buy one will get a bonus on their paycheck. That's about what you can expect from these people. Now, if you get really lucky, you might come across an actual computer
nerd who somehow ended working there because:
A) he just happens to be a computer enthusiast that needs to eat but not a pro
B) He's an IT like me but no place hired him because his qualifications are too high and nobody wants to pay him for what he's worth.
This guy might come useful if he's not too disillusioned and jaded but remember: he's got a boss to answer to. And his boss doesn't want him to give good advice; he wants him to sell stuff.
As I don't know how advanced a user you are in terms of PC's overall, I'll just give you my perspective as an IT guy in layman terms:
About Windows: let's consider Windows as a whole. It's a system, it does some amazing things really fast but... it's just software. And it certainly isn't an AI. It won't judge what you need or
not. All it can do is notify you when some dependencies are not met and only to a certain extent. You installing Daz Studio doesn't mean that Windows will notify you that you need more RAM
or better RAM. Think about it: if you install a weak GPU, DS doesn't tell you either "You should get a RTX 2060" or anything like that. You need, alas, to do your research upstream.
Rendering in Iray means that not only you need a certain amount of VRAM. Some RAM is required and the beefier the scene, the more it'll want too. Everything scales. The failure to render
is, in itself, your PC telling you "We're gonna need a bigger boat" :)
"That was fun. Let's do it again."