The grip is the same for both sumo and conventional deads.
One hand over, one hand under, arms straight down (no biceps). Coil down with tension to just reach the bar, don’t bend further and then jerk it. Don’t go one hand then the other. Get in position, coil down like you are lowering a weight, then up. The deadlift has no eccentric phase before the concentric, so it is important to coil.
Conventional deads are probably better for the post-chain, and should be prefered over sumo for athletics. Sumo are good if you have had a back injury or are doing powerlifting.
You can also do snatch grip deads especially if you are training the OLs.