1: it's good
2: why not?
Viewing post in Why are you using .7z format
It's as new as it can be, with the latest public beta release being a month ago. Don't be discouraged by the "outdated" interface (you can go for NanaZip for that, which is a fork of 7z) and website. And how outdated do you think Windows's implementation of .zip is? For all we know, it could be the same code from Windows 7 with zero changes. Thing can't even multithread.
Looks like you are not...
.7z, .zip, .tar.xz, .rar and e.t.c - they all old, they just still get updates.
7z best for saving space (~1.5GB into ~700MB 7z archive? not a problem), tar.xz best for linux and zip is just supported by literally everything.
There other formats like .wim, .gzip and e.t.c, but they used so rarely that there not 0 chance that you never see them in your live...