Looks like you can get high end itx motherboards like this one https://www.overclockers.co.uk/asus...-am4-ddr4-mini-itx-motherboard-mb-6c2-as.html
but there no high end micro ATX motherboards..
From the info given, the Strix ITX looks like it should be good... but I'm not sure I trust anything without seeing a PCB breakdown to work out what's under those VRM heatsinks. Reviewers are only now working out that things that look like 6 phases can be 3 phases with doublers. Which admittedly is better than 3, but it's not as good as 6 proper ones.
And no, there are precisely zero high end mATX AM4 boards. There are a number of low-midrange options, none suitable for a top tier CPU with an overclock. I don't think the manufacturers want to support an ecosystem where people DON'T buy a board with every CPU generation...