i'm gonna try and help as much as possible here:
generally freeride boards are on the medium - stiff side of the spectrum. because they're built for speed, stability, carving hard, and still being able to perform in powder. they're also generally good with jumps but not so much for rails. there are some out there that are regular camber but a lot of them are some sort of hybrid to perform better in powder. a lot of them also have a directional or directional twin shape. when you buy one you're gonna wanna go at least 4cm bigger then your park board. you being only 5'1" you have an abundant amount of options on your hands.
i wanna give you some boards to consider:
Never Summer - Heritage, Raptor, Premier F1
Gnu - Billy Goat
Lib Tech - Darker Series, Hot Knife
Capita - Black Snowboard of Death
Ride - Slackcountry, Highlife UL
K2 - Turbo Dream, Raygun, Slayblade, Fastplant
even though i haven't ridden any of these, i am not just recommending them out of my ass. in fact, if i was making enough money, i would become sort of a snowboard hoarder and i would buy quite a few of these without question.
one last thing, don't take my advice as the end all be all of advice. get advice from other people, keep doing research and try to get a general consensus on what you should get.