These are just my experiences. I shot snap for years but never got as good at paper, 3D, or hunting as I wanted. I'm a crank for accuracy though, so if the following sounds overly anal, you've been warned lol.
When I switched from snap shooting I had two main issues (besides all the other bad habits): 1. I was overbowed and 2. I didn't have a shot sequence.
The over bowing issue leads to collapsing, so as soon as I slowed down I lost tension and the shot got ugly. I spent a month holding and then dropped down in draw weight. I dropped over 30# in draw weight before I could really start holding for more than a few seconds without collapsing for multiple shots (from 85-90# down to 50-55#). These days I shoot 40-45# for everything.
The second issue reared it's ugly head not long afterwards. I had ingrained the shot trigger of letting go as soon as I hit anchor, or just after, and couldn't kick it. I later learned this is target panic. My brain couldn't decide what to do while holding at full draw either so my body just tensed up trying to be still until I would just flinch the shot off (anticipating the recoil). At this stage I could still "snap accurately" (or accurate for me at the time) and went back and forth for months without improving.
I eventually got over it by focusing on the feeling in my back while waiting for the shot to go off, like Rick Welch teaches, and my shooting improved. This worked on local 3D and in the woods, as well as on paper. However, I didn't understand what I was supposed to be thinking about/focusing on during the shot/release and it lead back to full-blown TP once I found myself under competition pressure.
After a year of that misery I started using Joel Turner's methods from MBB vol. 4, the feather to the nose and mantra. After the first month or so my shooting came back better than ever, with some of my highest scores and best performance in the woods. Unfortunately, I got pig-headed and started deviating from a focused shot sequence. It lead back to snap shooting but I soon realized that "snap accurately" doesn't work for me, and never did. I had gotten used to almost compounder-levels of accuracy on 3D and went back to Joel's methods. It's been a lot of work but that was several years ago and it's been a gradual, albeit sometimes slow, improvement since then.
No one can say what exactly works best for you other than your results. If I could offer one bit of advice it would be to stick to shooting paper for a while. It's honest and surprising- who knows, you might be a better snapper than gapper. Paper doesn't lie, and you wouldn't be the first! It's not for me though, and I wouldn't have known until I tested this stuff with scores and 3D in addition to my beloved stumps.
Like I said though, I'm a struggling self-taught accuracy crank, take all of that for what it's worth lol!