The question is then if I buy a combo from wootware and it does not run stable at advertized speed on a x470 mobo (apparently they tested but results might vary between mobo's, also this RAM is advertized as being for z boards so the tests must have been on one of those and are as such not completely trustworthy for x boards) will they refund?
Whao there, wootware does not sell combos or advertise X running stable on Y. You can return stock to wootware but they levy a 25% re-stocking fee.
Like I said google the mb & ram you are interested in and you'll be 95% certain whether the ram will work at it's rated speed, samsung b-die ram is usually fine. There are also ram charts out there warning against certain ram models that can use different chips for the same model#.