Hi @gsoper!
For a full rundown of how Arc Editor relates to Arc Timeline, the initial forum thread goes into detail: First public beta for Arc Editor!
Though the short version is: There’s zero risk, zero data loss potential, and the new app is better than the old app in almost all ways. It’s also very close to being final - I’m aiming to ship it to the App Store proper ideally before the end of this month.
The new app doesn’t yet have all of the features of the old app - I’m adding them back in in priority order of which ones people mention they’re missing the most. But it’s got enough in there now to be worth switching to entirely. At this point I basically only keep the old app around because it’s my job. Otherwise I’d have deleted it already 
The new app is so much better!
Oh, though definitely keep the old app around for a little while at least. There’s no need to rush to deleting it or turning it off. The two will run happily side by side - they record to separate databases.