Folder backup with incremental/differential, encryption, split archives ... WinRAR?

I want to backup folders to encrypted split files of a certain size. And periodically I'd do incremental or differential updates to that, with new split files with a different name (date).

Ideally I'd like a common format (zip, 7z, rar...) and/or something open source that I can use in the long run, but I'm not ruling out a proprietary solution.

The closest I've found so far is 7-zip. It does almost everything I want, the only problem is that it can't make differential backups from split archives. So I need to have a single 7z file as a base.
Another one that comes close is "BackUp Maker", it produces .zip files. But the zip headers (file names) aren't encrypted. And also when restoring the differential backups it doesn't remove the deleted files.

I read somewhere that WinRAR can make differentials from split archives, but I couldn't find a way to do it. What would I enter in the command line to set the *part* files as the base?

 

So I did some searching and it turns out WinRAR's "differential" mode isn't that great, because it relies on Windows archive file attributes (with -ac and -ao): https://x443.wordpress.com/2012/07/11/winrar-incremental-differential-backup/
The archive thing is "sketchy" in itself, because for example it's easy to accidentally reset it by just moving a file to another folder. In addition to that it means that a differential RAR won't include information about deleted files aka "anti-item" in 7-zip: https://sevenzip.osdn.jp/chm/cmdline/switches/update.htm

So from that it seems 7-zip is a better option for differential archives, unless you're sure that you don't mind the WinRAR limitations.

But I'm new to advanced WinRAR features, so please correct me if I'm wrong.

 

Have you tried DAR?
There's also a separate GUI available.

 

Thanks! I checked it out now and it looks like it has all the features I asked for.
Do you know if encryption also encrypts the file/folder names? It seems like it does, but I want to make sure.

Compression performance sadly doesn't seem to be quite as good as 7-zip's ultra/LZMA2 with any the four algos. Also the GUI is outdated now. But other than that it looks promising.