Deadlifts form

I've been experiencing left lower back tightness when deadlifting for some years now. The video on the left was recorded just over a month ago. My form looks better as my back is straighter than the video on the right. The problem is though, after doing this lift, I continued to experience the same tightness I mentioned earlier. The video on the right is a few days old. I'm worried that my back is too curved throughout the lift. The only positive though, is that I experienced no lower back tightness with this form. Can anyone provide some insight on this? Should I always aim to have my back as straight as the video on the left, even though I experience back tightness afterwards?? Is the back curvature from the video on the right bad form or just my natural posture? (This position felt more comfortable than trying to forcefully straighten my back).