This will help dictate some of your needs. Are you diving locally (lakes/quarries) or in the tropics? (the ocean). Will you be plowing thru cold water with non-aerodynamic (excuse me, HYDROdynamic) equipment?
Here's what I have seen & heard: a beginner has weak legs (yes, even if u run marathons, you have not built finning legs yet.) A moderate stiffness is smarter than a really stiff fin, but since you have a couple weeks, you can buy some fins & kick laps to strengthen your legs before the class begins, so there is not really the need to go for a super easy-kicking fin.
Why work hard to build muscle? To stay warmer! If you have more muscle in your legs, you will be more resistant to cold, more negatively buoyant (needing less lead to sink u), and be more able to walk with equipment on your back. You will have less cramping with a well-conditioned leg.
Some of your needs may deal with your foot shape. Will you need a wide or narrow booty? Are you diving in rocky areas that require a tough-souled booty, or off of boats where a thinner soul is fine? Fins & booties gotta fit together! I hear a lot about LDSs telling newbies that if they are "serious" they should get some crazy new design. (Strangely, they never suggest anything cheap. Hmmm...) I like vented rubber fins. My husband (a fin junkie) likes non-vented rubber fins best. Most people I dive with like those Cressi frogs (plastic, but with some rubber panels, I think). I can't stand all-plastic blades. Have not tried splits. Have seen some newbies happy with them in the pool, but don't know if they will accelerate fast enough for the ocean.
Whatever you choose, you are going to have to put some focus on training those legs to have a relationship with the fins. Many people get new fins before OW is even done, so I never tell anyone to blow too much $$ on them. You will learn a lot by switching with classmates in the pool to see if anything works better for you.