My issue is that if I want to keep my back straight and actually use leg-drive, I sit with my ass parallel or below to the floor. I have short legs, and a very long torso with short(ish) arms. Sitting like that dramatically reduces the amount I can pull because it almost becomes a full squat trying to get off the floor and is very uncomfortable. Just being in that position fatigues my legs and lower back. And obviously, I cannot squat as much as I can pull so this is sort of a problem.
FWIW, I had this problem for ages (combined with slightly shorter legs, slightly longer torso), and am currently working to correct it, which is going very well. I had to reorient how I thought about the deadlift in general in order to correct the form, as well as drop the weight until the movements started to ingrain themselves.
I'll start by saying that I am in no way an expert, but this is where I've ended up after years and various coaching, and I find this preserves my lower spine.
When I've set, bar over laces with shoulder width stance, I bend down naturally with hips/knees, and grip the bar so my elbows are touching my knees sort of on the outside. Then I put on tension just to get the feel, I do this by anchoring back into my hamstrings and glutes while tightening my core and sort of "crunching my lower abdominals forward" if that makes sense, which sets my back and keeps it where it should be. From there I keep all that going and just take the big inhale into the gut, hold it, squeeze my shoulder-blades back, and power the heels down from that anchored position. I focus on putting as much pressure into my squeezing core as possible and once the bar is most of the way up my shins I push the hips through while maintaining the shoulder-blade squeeze until I've defied gravity.
I experience no rounding or undue pressure on my lower spine with manageable weights (~315) for low reps, and I plan to continue this and not push it until I feel comfortable upping the weight and going for PR's. I do high volume stuff with ~225lbs during crossfit workouts sometimes, and this really helps reinforce the movement. My previous 1RM with a shitty conventional form was 495@230 body weight, I plan to eclipse that poundage at a lower body weight.
I was pulling sumo for a while, before getting into this current conventional groove, due to it having less impact on my lower spine, but there just is nothing like the feeling of a conventional deadlift when done properly. Squats, Deadlifts, and overhead presses = Crom worship