Most dogs can learn recall on an e collar with a fairly skilled person with out any trauma or upset. You are calling it a shock collar. But it does not have to be "shocking", frightening ect to work. You do have to keep the dog on a leash or a long line until they truly get it, I prefer to proof all the real life situations with a long line and if I don't need to use the long line during all the levels of proof then I am ready to let the dog run again. For me that meant I had to find a deer and call him off it successfully before he got his offleash privileges back, I use the collar like this: I apply the level that is just irritating enough that the dog is not willing to stand there and tolerate/ignore it, but not so high you are getting vocalizations (yelping), tail tucking, stress or fear response.
I would call my dog pretty soft, when he gets corrected it is pretty mild. But with w good e collar like a Dogtra, you can be as soft as you need to be in the dog. I wouldnt train with a 10 level e collar because the jump between levels is so high that you can't be sensitive enough.
I understand wanting to let your dog run free, I think my dog was on lockdown for 3 weeks or a month before I had found all the things I wanted to proof (turkeys, deer, ect). He was showing great understanding of the collar but I wouldn't risk him running through the stim because if I chose the wrong number and he wasnt on a long line that could happen. If they ever learn they can blow through it and take the hit and then chase the game you are in big trouble, sucking it up fir the lockdown period is worth it