Yes, it's basically faster than disk swap but uses some CPU cycles. The compression algorithms involved are very fast on modern CPUs so in some sense it's "free RAM".

I set mine to almost 1:1 my physical RAM, because the way it works is that the zram disk size (62.6G there) is the amount of uncompressed data allowed on it, and the compression on real-world data is almost always at least 50% -- so if the zram device fills up, it'll be using something like 32G of physical memory. I'm yet to hit real-world usecases that would have tested these limits though, and the defaults are much more conservative.