In addition to that, Ryzen like fast memory in dual channel. These is worsen with igpu also heavily influenced by the same factors. It possible that the memory in the system is in single channel(or only have 1 stick). A lot of prebuilt tend to use only 1 memory stick . While it might cost a little bit adding a other memory module or check if there 2 if they are install to benefit from dual channel memory. If you running 8gb of ram you would likely benefit from 16gb at some point at some point. You igpu is likely to be affect more by this. It might seem small but my main laptop using a i7 7700k and intel hd 630 the extra memory stick did make a decent difference for the integrated graphics, if I remember right the igpu was able to do 2x in mario kart and the vega igpu should be decently faster. The laptop also has a gtx 1070 also but it wasn't affect by this if that used nearly as much.
I use a r7 3700 and r9 5900x and both have no problem with mario kart with reasonable graphic card (gtx 970 for the r7, rtx 2070 for the r9) or most games outside of the most demanding games like rogue squadron 3 and the like. So the processor using zen 2 or 3 isn't the problem. Core count wouldn't matter either since even 6 core is more then enough also.
I use a r7 3700 and r9 5900x and both have no problem with mario kart with reasonable graphic card (gtx 970 for the r7, rtx 2070 for the r9) or most games outside of the most demanding games like rogue squadron 3 and the like. So the processor using zen 2 or 3 isn't the problem. Core count wouldn't matter either since even 6 core is more then enough also.