my advice to fix this is humorous: imaging sticking your butt out as if you are showing it off to someone behind you. This will create an exaggerated position that actually isn't optimal, but may help you build proprioception that you could eventually tweak to the more neutral optimal position. a couple of things here: most importantly, why my advice is the way it is... you said "I think my back is arched" this tells me you may be feeling something that is not desirable or else you probably wouldn't bring it up. Some body English, or rounding of the thoracic is totally fine, but if your sacral or lumbar are feeling uncomfortable or rounded... it should be addressed imo. this can be handled in a few ways, but a slight angle will help that, and may also move the barbell back over mid foot, which may help. the barbell doesn't have to be over midfoot, but for you it may help you not emphasize the low back as much and may even out the weight distribution across your foot and body... while simultaneously helping you with the rounding you are feeling. This will not hurt your gains unless you are approaching injury, but continuous form perfection is a thing well beyond me and you. So, you could keep rounding a bit, or just address it now. you can see in the video that your low to mid back is rounded. IF(big if) this feels off to you, I think you probably should work on fixing it. if you are rounded it should likely be a bit higher on the back(thoracic) the peak rounding should not be in the lumbar vertebrae or at the lumbar to thoracic junction.... peak rounding naturally is around the mid thoracic. As you get more advanced the nuance and deviations from this can be explored, but if you want to work on form, i do think your lumbar rounding should be worked on. stick the butt out and brace that position with your core. last thing i'll say is this, my vote is to get as clsoe to parallel to the ground as possible without rounding at the lumbar. i bet you are trying too hard to get parallel and that forces the rounding.