A partial answer
Yes, if the pistol is marked .38 Super or Super .38, it's good with +P ammo. In reality, Super .38 is the Plus P version of the old .38ACP cartridge. The two are dimensionally identical. The old .38ACP, loaded so as to be safe for the older, parallel rule lock, double link pistols, was much like the 124 gr. 9mm Luger cartridge in power.
With the advent of the Super .38, in 1929, the ammo was a couple of hundred FPS faster than the .38 ACP. Full power Super ammo might or might not BLOW UP the older design pistol, but it would certainly ruin it in short order.
If the ammo is marked "Super," then the "+P" means nothing, really. In recent years, Super .38 ammo has sometimes been marked as such, and sometimes as ".38 Auto +P." If you run across some old "Standard" .38 ACP ammo, you can shoot it in the Super .38 pistol - - It's kind of like shooting .38 Special in a .357 Magnum revolver. It's just unsafe to go the other direction.
As to the finish on the current RIA pistols, I doubt they use a "Hard Chrome" on them. Far more likely it is conventional nickel plating. Sorry, though - - I have no first hand experience with the silver-colored RIA pistols.
Best,
Johnny