In response to your question about can you install Windows and Ubuntu without creating a separate partition: No. You would end up corrupting the data of the other operating system upon installation (and im sure it would lead to lots of issues if it were possible to do it after installation).
However, creating a separate partition comes at no cost. Simply create two partitions (one for windows and one for ubuntu). Install windows first and then ubuntu because ubuntu will automatically configure grub boot loader to work with windows without any hassle if you do it in that order. If your windows partition is already made, you could resize it to make it smaller and create a new parition for ubuntu and then install ubuntu on that new partition.
To answer your question about the size of your Kubuntu install, when you are installing it, you can make the partitions bigger/smaller and that will dictate how much room you have for your linux OS.
Also for the future, it is good practice to title your question more specific than "can you answer this question for me". In the future, I would recomend something along the lines of "is it possible to change partition sizes when installing Kubuntu and can i install it on the same partition as windows?"
df -h