I have installed 3 ponds over the years and learned much from all of them. Currently have a 22' x 14' pond in the back. Biggest concerns are:
1. depth
2. light
3. water movement
If it isnt deep enough it can freeze through in the winter killing everything. minimum is 24" but I know most kits are 18" deep.
If you can its okay to put it under a tree so a bit of shade goes over it, preferrably an evergreen so no leaves fall in. If you have water lillies for shade, go treeless
Water movement is crucial, you will end up with a pit of algae unless you can move and areate the water
I would say, really, if you have a kit, take it back if you can. Its just like tanks, the bigger the more stable it will be. I would try for a 30" deep with a flexible liner in whatever design you want. Also if you free dig it with a flex liner there are tricks to make it easy to care for
If you want any other info or want help in the planning just let me know
Good luck