I thought rectangle was the next evolution of spectacle

It is, since Spectacle is no longer maintained. Rectangle is linked from the Spectacle README on GitHub: "Spectacle users have recommended Rectangle as an open source alternative."

https://github.com/eczarny/spectacle#important-note

The Parallels Developer edition comes with a pretty great window snapping feature. Parallels was the only solution to run Windows on my M1 Mac. In addition to doing a great job at VMs, it comes with a bunch of handy utilities.

I got Parallels in a bundle deal and was really aggravated by the fact that it kept popping up notifications to install additional utilities. Way uncool.

Yes, so agressive, stopped using it because of it.

Is it the same developers. My main gripe is the complete change of key commands and the option to swap to Spectacle key commands is very limited.

Spectacle was created by a different developer. Rectangle contains nearly everything in Spectacle, and it includes an option when you first start the app or when you go to reset the default shortcuts to select the Spectacle shortcuts.

it is. Spectacle is no longer supported.

I still use Spectacle! Maybe I'll abandon it if I ever upgrade to Big Sur -- but it continues to work for me.