For the sauger, being that you know how to catch walleye, you will catch your first and second maybe 10 and think it is cool, then be annoyed by them... They are basically the panfish of the rivers. I like catching panfish, so no disrespect to fish that bite, but you will figure them out in about 2-3 weeks. Depending on flow, 1/16-1/4 oz jig head with curly tail, paddle tail or V tail plastic in white or chartreuse or whatever color seems to be the trick will often catch you a ton. Morning or evening ups your odds now, but in a few weeks won’t matter. If you are within a mile of a dam, they will be there. Or mouth of creek. Flathead minnows will work too. But for most, they are the fish that steals your bait when fishing for eyes.
For the gar, can’t say that I have targeted them ever. I have caught. They are hard to hook. When around they are fun/frustrating. They hit like piranha if something is close, but hooking and getting to you is like 1:20. I have heard of guys that do target, something to tangle their teeth helps land them, I personally have never done it. I have caught them with a lot of luck with plain hooks, using a wood bobber and shiner. So pretty sure they stay higher than sauger/walleye. If I were looking to catch one, I’d fish below a dam and figure out some sort of mesh/frizzy cloth contraption right next to my hook, tied on or stays near, with shiner, and maybe 18” of line to a wooden “launcher” bobber. Cast that into the wash of the river dam outflow, fan cast around until you find where the gar are hanging out. You can have a blast if you figure it out. They school up and attack your stuff. Nonstop action for a while if you find them. But can be 20 bites and have maybe 3-4 hooked for 10-20 seconds, maybe get lucky to get your hook wrapped around its snout. I doubt that very many landed gar are actually stuck in the top or bottom jaw. Google techniques and I am sure will give you better odds.