You will also want to change the default settings in Remmina for:-
Colour Depth. Set 24 or 32 bit. the default 8 bit is unusable
Depending on the target and your own Screen sizes some experimentation may be required.
The Remmina Scale Mode works very well, and allows you to fit ALL the target screen into your Remmina RDP Window.
I found creating some Custom resolutions was very handy, to create a window which fits nicely on my screen without scrollbars, and then use Scale mode to fit the target into that.
EG on my 1366 x 768 screen, I use a custom resolution of 1024 x 640, which gives me a window that fits my screen leaving the Unity Top & Side menus visible, along with a bit of space to reveal windows of other apps.
The Group Function is handy if you have many target systems. In my case I create one for each of my customers, and then group machines by customer.