Bags or rest, one is pretty much as good as the other. The rest is adjustable but has hard points. The front bag is kind to your range box but one size doesn't fit all benches/positions. I have a fairly cheap rest and rear bag. It works well for me. I'd suggest you get a rest for up front and a bag for the rear. A few plain sand bags might serve you better then a bunny bag. You can stack plain bags if you need more hight due to an uneven bench or different firing position. Just get the best you can afford. Mine works but if I could have spared the cash I would have bought a more solid model.
A sled looks like an option for load development. I can't say from experiance but it looks like that's about all it's good for, and a bag/rest combo will do the job and be more versitile.