good for you, great choice!
In a J frame and .357 Magnum you have three hammer types, Chief's Special (standard exposed hammer with spur), Bodyguard (shrouded hammer), and Centennial ('hammerless'). You can have blued, nickel plated, or stainless in a full-weight or you can have AirLite titanium/scandium.
A little larger frame was the old K frame, many people's favorite.
The L frame replaced the K as the 'medium' frame, it's a little larger. You can get them with 7 rounds.
Then there's the N frame, the large. The 27 was the original .357 Magnum before they had model numbers. You can get more recent ones with 8 rounds.
In all the larger frames you choose whether you want adjustable or fixed sights, there are some of the J frames with adjustable but mostly fixed. The small guns are not the best choice for target shooting, so that's usually the right choice.
Of course you know you can shoot .38 Special in any .357 Magnum, and most of your shooting is likely best done with .38. These guns have no problem with dry-firing, they're the best choice for that.
Around '82 they quit making the pinned barrels and (on magnums) recessed cylinders. Finding good old P&R Smiths is my favorite thing to do at gun shows. They're better than the new ones and cost a lot less.
S&W has recently started making a hammerless J-frame and calling it a Bodyguard. This confusing use of terms they've used in the past for other meanings is not part of any of the above. A Bodyguard traditionally is the shrouded hammer, where there is just a pad of the hammer exposed so you can cock for single action shooting if you need to. This is a silly thing for a pocket gun, I much prefer the Centennial, completely hidden hammer for this. The 640-1 is an outstanding hammerless, stainless, Magnum pocket gun.