I don't know the details behind Synology's Active backup for Business; haven't used it before. I have used Synology and Xpenology stuff before for some clients. That being said, Synology is mostly Linux based under the hood, and many of their "applications" are simply Linux open source projects that they've bundled neatly together with a UI element within their "ecosystem"... so, that usually means, whatever they are offering, there is probably an open source equivalent to accomplish the same thing. But, what is different is that they've packaged up those solutions in a very nice and neat manner with a simple UI to make it easy to use. If you find out what open source project they are using in the backend, it many cases you can still accomplish the same technical requirements, but require a lot of work to get it working right for you. Generally speaking, that's the trade off going from "synology ecosystem" to "Linux" solutions... the technical requirements are usually achievable both ways, but unless you're Linux savvy and comfortable reading How-To guides, man pages, technical docs to figure out how to get the open source solution to work for you, it can be a lot of work. This is coming from a guy who has worked on Linux servers for over 20 yrs.... in fact, I run my own CentOS 7 servers and do a lot of the things you mention and more, but i've been doing this type of stuff, implementing open source solutions for businesses for a long time.
BTW, what is the motive to leave Synology? (since it sounds like it works for you?...)