That’s one way to do it. For me - I managed to double my upload speed by using a VPN (not gonna give its name here so it doesn’t become an “advertisement”)
Another important thing is to make sure the region (of the B2 account) is as close to you as possible : i.e. US if you’re in the US, europe if you’re in europe (or close to it), etc.
No, that’s the way the de-duplicative backup process of Duplicacy works: it chops up files into “chunks” so that it can more efficiently prevent full re-upload of files that are too similar (or identical) to files that have already been backed up.
When you restore the backup - you will see the actual “file tree” hidden behind all these chunks and would be able to choose what to restore and where to restore to
If you want the files to exist “normally” in the destination you need a copy or a sync tool and not a deduplicative backup like Duplicacy.
It is my understanding that the backup process can be paused or even cut off in the middle and then resumed (but maybe more knowledgeable people can give out more accurate info).
I personally have stopped the backup many times in the middle and then resumed and all seemed to be OK.