WinSCP matches all your requirements.
Graphical: Yes – There are two alternative interfaces:
Feels like a Windows explorer window: Yes – One of the interfaces is explicitly designed after Windows File Explorer.
Supports drag and drop: Yes – Both between file panels and between other applications.Uploading via ...
I have used the 3 following FTP clients during the past years so here is my feedback:
WinSCP: the one that I currently use. There is a portable version, just one .exe file (and the .ini file for configuration). Don't forget to turn on the "Explorer" interface:
View > Preferences > Environment > Interface > Explorer, which is (IMHO) handier.
Benchmark: it ...
For me Cobian Backup 11 can be installed in Russian language, and it compresses files with cyrillic names without problems to zip or 7z archives.
Also, try configuring the system locale to the correct one. You can find a lot of tutorials how to do that.
Actually, there're many apps/services that can do the backup like CloudHQ, Cloudsfer, cBackupper... CloudHQ and Cloudsfer are like cloud-to-cloud migration and cBackupper is more relevant to what you want, the cloud backup thing. Besides, cBackupper also has the PC-to-cloud backup mode, but it seems like this function has not been released yet.