Try to learn the monokick with bifins first. I think you will benefit from this since you will get the balance thing going and such. There is a lot to learn practicing the monofin with bifins, and i think it is the smart way to go. Starting off with a fin that is to heavy or advanced can play tricks with and ruin your technique which may be hard to correct later on.
I would suggest to get a monofin with an angle. It is not everything, but i prefer it anyway. As for having one fin for constant and one for dynamic, it all depends on your needs. I think it is smarter to start off with a fin that can go for both, but i do not think you will find one that is perfect for both if you are going advanced. Maybe a fin that will be good, but not perfect. However, as long as you do not really know how monokicking feels like i think the way to go is:
monokicking with bifins ----> getting a less advanced fin ---> move upwards depending on need.
Good luck!
I would suggest to get a monofin with an angle. It is not everything, but i prefer it anyway. As for having one fin for constant and one for dynamic, it all depends on your needs. I think it is smarter to start off with a fin that can go for both, but i do not think you will find one that is perfect for both if you are going advanced. Maybe a fin that will be good, but not perfect. However, as long as you do not really know how monokicking feels like i think the way to go is:
monokicking with bifins ----> getting a less advanced fin ---> move upwards depending on need.
Good luck!