Never new exactly what a matx was but after googling matx cases and quickly googling am4 matx motherboards my options are endless on what spec components I can have, graphic cards options is a lot better and maybe it will work out a little cheaper than buying and building a itx gaming system and being limited on what itx mini graphic cards there are...
So in order of size itx is the smallest, matx then atx being the largest..
Good little learning curve and great advice and now my options has broaden ty