Before I learned about bare-shafting from Dan Quillian, I experienced frustration when my "perfect" arrow flight with field points turned out to be not so perfect with big broadheads. In fact, they sometimes dove into the dirt at 20 yards! I would end up using narrow two-blades, because they were the only ones I could tune to.
If you are within 5-10# of the correct spine, your field point accuracy can be good and your arrow flight can look perfect. The big broadheads tell the tale. All the problems went away when I bare-shafted and found out I was a bit underspined. Now I don't tune without it.
Often if you're having trouble bare-shafting, it relates to getting the brace height right and the nocking point right before trying to find the perfect spine. I just went through that tuning a Super Kodiak. I wasn't sure where to brace the bow, because it's been a decade or so since I shot a Dacron recurve, but once I found that 8 5/8 - 8 3/4 worked well, then I could locate the nocking point, and everything went smoothly from there. The old relic wants 80-85# shafts with a 50# draw! I wouldn't have believed it needed that much spine until I did the tuning, and it's now shooting several different broadheads perfectly.
Narrow two-blade heads are the easiest to tune, since they can be off in spine a little more than a big three-blade, but accuracy is best with the perfect spine, and any broadhead in the same weight class will shoot well regardless of size or shape when you get it right.
Good form and a good release are important to bare-shafting, but you don't have to be perfect. I shoot repeatedly, and look for the average. After decades of bowhunting I still am not perfect in my release every time. If I flub the release, I just shoot again and again until I've see the arrow doing the same thing most of the time. I eventually get there.
Good form and a good release are just as important when the arrows are fletched, especially shooting broadheads. Practice makes perfect!