When I am calling, I strictly use cottontail or jackrabbit distress. I have used howls but I am way more successful with rabbit calls. As already mentioned, howling depends on the time of year, weather, population in the area, everything comes into play whether you will scare them off or bring them in.
When I call, I call for a maximum of 15-20 minutes in an area. in my experience, if they dont come in by 15-20 min then they arent coming MOST of the time. This rule applies for young 'stupid' coyotes. the old big ones are old and big for a reason, they are the smartest animal in the woods and hard to trick.
Stands can vary. Im not a long range shooter so anything over 200 yds is not for me when it comes to hunting. Where I hunt in the hill country/south Texas, most of my hunting is in thick brush and mesquite. I often hunt with a shotgun. I have on multiple occasions had a young coyote come sprinting out of the brush less than 10 yds during my first call string. either iron sights/aimpoint or a shotgun is your only hope here because the second they bust out and see you they turn and run just as fast as they appeared.
Keep the wind in mind. this was already mentioned as well. Remember, older experienced coyotes will circle the area before coming in further to investigate. watch these avenues. if possible, put a body of water, large open field (in daytime, I have never seen a healthy coyote expose himself in that big of an open space) or another obstacle behind you and downwind so they dont get in the cone.
Unless you are going to try for them at over 2-300 yds, dont overthink your weapon. Carry whatever rifle you want. I use a non-free floated 14.5" M4gery with an ACOG or aimpoint that I use for literally everything...hunting, home defense, duty rifle etc.
Have fun with it! good luck