Well I just bought the 3-18 from outdoorsman (I'd recommend them since you get a free custom turret). So I can tell you what I learned in my consideration.
I'd stick with lower magnifications especially for elk. They are big and easy to aim for vitals. Also, I have a 7mm rem mag as well and with that recoil you will have a hard time getting back on target (seeing the elk) at a higher magnification. I've heard 15 is a sweet spot but others have even said 10x. Depending on the reticle, your reticle marks are usually based on the highest magnification in SFP if that's important for you to use holdover.
If you want to use your scope to judge the elk, then higher magnification may be the way to go and then dial back for shot and you can still learn the holder I guess.
I went with the 3.5-18 since I wanted it to be versatile. I missed a bear at 30 yards because my old scope was 6-24x and FFP. So I like having the lower magnification for those surprise moments and 18 is plenty for me shooting up to 500-600 yards on vitals. If you want to target shoot and at longer ranges, go higher.
Hope this helps.
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