A lot of people say that the R70x sounds better with a dedicated amp, but realistically you don't need to spend that money if the headphones are loud enough and don't have pick up any noise from your motherboard. This is a bigger issue with cheaper/older components, I have an Asus x570 board and the dac is shielded from noise quite well (I still use a headphone amp but that's just because I enjoy it, not because it's a requirement).

Hardware dependent for sure. I have a decent x570 mobo and there's no noticeable difference in noise/clarity compared to my DAC and amp, but not all motherboards are equal in terms of shielding.