The basis for the editor is my open source drawing plugin for leaflet - Leaflet-Geoman.
It supports circles because Leaflet supports circles. GeoJSON is just a format to export Leaflet-Layers - so we made Circles work even though it's custom.
You're definitely right about the unit-less part. Something I should be fixing.
They will come soon. No paid features planned yet but we will see how much effort the tool is for us in the future. For now, most of these formats will be supported for free.
Good point. Performance is a problem on these tools and I need to do some work on that front as well. My email is on geoman.io - send me a data set and let me try. I will make improvements here in the next weeks.
ONSITE in Berlin or Stuttgart (Germany).
TL;DR:
car2go is hiring || FRONTEND (REACT, ANGULAR, VUE), NODE.JS & RUBY ON RAILS devs.
Process: talk to me, get an invite & talk to my boss, hired (or not).
If you want to know more you can hit me up on twitter: @TweetsOfSumit