I'm a die hard 357 magnum guy, there are some 38 special loads that I do trust but if I'm only carrying 5 or 6 rounds I want the best performance I can get. A 38 J frame is good for pocket carry and a good back up gun but for an EDC revolver I want 357 myself.
Accuracy is very important, In my experience finding the right grips that fit your hand is key to controlling the 357. As for flash and blast that can be powder and load dependent. My last range trip I shot a cylinder of the Federal 38+p FBI load, it had way more flash than my full power 357 hand loads, 13.5 grains Accurate #9 with a 158 grain SWC. Newer defense rounds especially will have flash suppressed powders. Let's not forget having a 357 really opens up your options, even if you find full power magnums aren't the best idea there's always the lighter 357s like the Golden Saber and Gold Dot Short Barrel and the hot 38+p loads from Underwood and Buffalo Bore. These loads will have better performance than your run of the mill 38+p and at least get you into 9mm territory. Any time someone asks about a 38 revolver my advice is go 357, even if you only plan on carrying and shooting 38s it doubles your ammo options and you'd at least be able to use 357 in a pinch. I love the 38 special but as part of the whole 38/357 package, I don't own any 38 only revolvers anymore.
I think you're on the right track, a 3 inch K frame is a very good carry magnum. I don't have a K frame but I do have a few of the Ruger Six series revolvers which are the same size, they even fit the same holsters. IMO a 3 inch 6 shot medium frame 357 is the perfect carry magnum. Small enough to conceal yet big enough to control full power 357s, the 3 inch is no harder to carry than a snub and it has enough barrel to get the 357 up to speed. Here's a review I did of my Speed Six and explaining in detail why I think "combat magnums" are the perfect 357s for ccw. If you enjoy it like and subscribe please!