I would love a comprehensive answer to this as well. The documentation shows how to do each, but says nothing about why to choose one or the other.
It does specify that bridging is L2 and managed routes is L3, so I think you’re right about broadcast differences but I’m not well-informed on that subject.
As an aside, did you not need to enable the “Allow ethernet bridging” option even when using managed routes with your Teltonika router? The guide for doing this with an OpenWrt router is very explicit about enabling that option and I’ve never even tried turning it off to see what happened.
https://github.com/mwarning/zerotier-openwrt/wiki
https://github.com/mwarning/zerotier-openwrt/issues/112#issuecomment-1516000533