Can someone explain to me the difference between Bottles versions?

I can't install the latest version of Bottles because I don't have space on my PC to install Flatpacks (it's like 5 GB!). I can however install the currently maintained version of the v1 Bottles. But it isn't clear to me how it's different from the latest Flatpack version. And I did try searching it but I got nowhere fast.

Perhaps someone can tell me how this works?