Everything I've done lately has been with a site called Cute Cutter. https://cutecutter.com/
It's like you said with what you're using. You can upload a picture, preferably close up and as high def as possible and adjust a few setting it has, called blur, edge contrast, threshold, and remove speckles, but it only gets you to a starting point. Then there is a slide adjuster that lets you transition the image from the original to the pattern where you can see both at the same time and you make adjustments manually with "touchups" I didn't have a teacher, just played around with it for hours and hours with my laptop while sitting with the fam watching TV. Very very often I give up on a picture because it just doesn't work well with this program. I'm sure there is much better software out there and I'd love to buy something, I just haven't really done much looking. This site is free except I make a donation from time to time. You're also limited with fine adjustments with this site and sometimes when I've done all I can do I download it and make adjustments in Paint 3D. I might actually spend 4 or 5 hours on a pattern so it's tedious but I enjoy it as much as cutting sometimes.