9x19 is the 'Free West' cartridge size aka 9 mm or 9 mm Luger, all the same.
9x18 is the 'Eastern bloc' cartridge size aka 9 mm Makarov.
You shouldn't mix em up.
Grain is the bullet weight and very simply put, with the same powder charge the lower grain (lighter) bullet will be faster then a higher grain (heavier) bullet.
There are a lot of abbreviations indicating the composition or shape/properties of the bullet.
Some are here:
Lot of things considered it is generally accepted that some sort of hollow point is better suited for personal defense.
However not all brands of hollow points load reliably in every type of gun.
This has to do with the shape of the bullet nose and the angle of the feed ramp and that sort of stuff.
Buy a box of several different brands and find which ones work best for you.
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