Right. The New Vaquero (not "new model Vaquero"!) is a new gun built on a mid-size frame capable of coping with the 357Mag but NOT 44Mag.
The larger-frame series Rugers (including the "Old Vaquero") was built on a 44Mag-class frame. Hence, when chambered in 45LC you could go really wild with it, in some cases exceeding 44Mag horsepower levels by a tad.
The New Vaq can be fed any load in any caliber that a Colt SAA post-WW2 can cope with. A Colt SAA can take all factory 357s, therefore so can the New Vaq (which is *maybe* 10% stronger than a real Colt). In 45LC a Colt SAA can take 255gr lead rounds doing 1,000fps or so with either strong factory ammo or careful handloading. Or it can take 200gr jacketed at around 1,100ish. These are thus also the proper limits for the New Vaq.
I own one in 357 and love it...while not as crazy-strong as the 44Mag-class, they are better made to finer tolerances and at least on average are more accurate than their bigger cousins.
So far only one adjustable sight version of this frame size has been made: the 50th Anniverary 357Mag Flattop Blackhawk. All other post-'73 Blackhawks are on the 44Mag-class frame (regardless of caliber).