We once fostered a Chihuahua who was trained on puppy pads, but would still have off-the-pad accidents and never got the hang of going outside either. He acted like it was okay to go off the pads as long as it was "on" something: towel, rug, shirt

left lying in the floor.
When we got Madddie, I knew I wanted her to go outside so I crate trained her to always go outdoors. I was afraid allowing her to potty inside sometimes would allow her to think it was okay. I didn't want potty in the house at all. She was easy to train and never has accidents.
Cooper, our rescue, was pad trained at first then left outside all the time or left in a taxi all the time. She is so confused on where to go.

She is 8 months old and still has accidents in her crate, the floor, but will go outside on cammand too.

We have had her for 5 months and work consistently with crate.

All that was to say, in my experience sticking to 1 method of training works the best.
Also, I always to out to suppervise them. I am to afraid of stray dogs, where I live, loose dogs from neighbors, or wild animals. It only takes a second for something to attack and take them, Just not worth it to me.