deadlifting ?

what's the benefit of using an over/under grip? i always use an overhand grip with both hands, i've tried using over/under a few times and while the lift seemed a little easier, the bar swayed a lot and was difficult to control which freaked me out

The benefit is what you mentioned- the lift seems easier because there is much less of a strain on your grip. If it was getting out of control on you, I don't know, maybe you were using a really narrow grip?

possibly, i haven't done deadlifts in a little while actually, but i recall using a shoulder width grip, maybe slightly narrower

You just have to get used to it..

But I figure unless you're training for PL or something, go overhand and use straps on max sets.

Then just train the shit out of your grip separately.

I would advise you to never use straps (or belts, or any other

If your grip is narrower than shoulder width, I assume you are using a
sumo style deadlift, which is fine. If not, your arms should be outside
your arms which I believe would neccessitate a wider grip. Good luck
and keep pulling.