I don't think a low end card is going to give you any idea of what davinci is like in the criteria you're considering. If you want a stable, well performing, capable system I would look carefully to the config guide. If you want to test drive a system with an eye towards how well it would work for you, I think it would behoove you to hire a proper resolve room for a day to test drive it. Preferably with someone there who is willing (and paid ) to show you how it works.
Performance on a non optimized system is not indicative of what resolve is actually like,
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