Can I play Minecraft smoothly with an AMD Vega 8 (iGPU)?
if so, how many FPS do he have
YES is enough
IGPU in 2020? Critical. Even for MC. So without a TP-Pack and shader you can probably do it, but if I were you I would take a GraKa.
This is the Bedrock version that eats almost no performance for Java, I would recommend a GraKa. But I think IGPU is playable too.
The mine is almost irrelevant to minecraft, the ram and the processor are important
That's enough too