That's a good mini ITX case, congrats. And the PSU is rated for 450W, right? It will be more enough to power your system.
As for motherboards, I wouldn't go with AM5. As far as I know, there are only 3 mini ITX boards right now and they go from expensive to very expensive. AM4 and s1700 have far more options with a wider range of prices.
Please excuse my bad English.
Currently gaming on a PC with an i5-4670k@stock (for now), 16Gb RAM 1600 MHz and a GTX 1070
Steam / Live / NNID : jonxiquet Add me if you want, but I'm a single player gamer.