Does this style of leaves look appealing?
Yes! Yes it does! With most of the trees being the same shape, I like how this one takes a different approach to the shape while keeping in the same style. I do think @spikeyxxx ‘s critique is a good one though and I agree – they’re slightly too flat overall. Perhaps just a couple sets of leaves sticking out at odd angles would be enough to make it look just a little bit fluffy.
For the shading, everything looks quite good but I would really prefer to stay away from emission shaders unless it’s critical. Try using translucency or SSS instead so that the lighting will always match all the other objects in the scene. If we need to tint the shadows a certain color like that (to change the time of day, for example), it would be way easier to change the environment light then dig through all the shaders for all the objects in the scene.
On the optimization side, please put the alpha for the leaves into the alpha channel of the color texture – the fewer textures to load the better. If you can find some other way to add variation than multiple leaf shaders (like vertex colors), that would be preferred. Similarly for the bark, try baking all of this to just one final texture:

The bark texture itself looks stellar.
Amazing work here, and full points for week 3 and then some!