Where are you located? We get a fair amount of smow here, so added weight can help. But usually you don’t want a lot because it affects your gas mileage badly. Have you driven in snow much or at all? Fishtailing and sliding on snow is usually from trying to go too fast for conditions. Slowing down, sometimes to a crawl, for curves, turns, stopping, will usually kept the vehicle under control.
Ice underneath the wheels changes EVERYTHING!! Weight in the back won’t help there, you just slide further, faster, spin out.
I carry about 200#s in back of the 2WD truck. A 2x10 board is behind the wheel wells to hold bags of sand or rocks in place by the tailgate. No load sliding forward with a hard stop! Other folks I know may carry a flat sheet of steel in the bed for weight, couple hundred pounds. Steel doesn’t get in the way of picking up a load of grain or “stuff” that needs moving.
I also carry a small shovel, square shape, in case I need to dig out the truck. Small so it does not take up much room, makes you take small scoops while digging out the wheels to NOT over exert yourself in the cold. An old trick is to throw the snow you shovel into the truck bed. Snow adds more loaded weight, is cleaned out from under the wheels, making it easier to just drive away from where you got stuck.
Do not BELIEVE that 4WD is going to save you in winter. EVERY ONE needs to slow for conditions, slow down and stop straight, THEN make your turn, so you do not spin out. Locally, those who think 4WD means the rules don’t affect them, are the folks who race by us, then we see off the on the side of the road stuck, or way out in the median between lanes! I honk and wave! They will need a tow truck to get out, 4WD alone won’t get them out of that. The best tires won’t grip on ice, packed snow when you are going too fast. Inertia will just keep you going. 4WD can help keep control of the truck, but it won’t make you immune to weather issues, so save it as a last resort. Slowing way down will better help you stay in control oF your vehicle.
Best of luck with winter.