One time purchase
I would love to know if one time purchase is available with all features.
Sort of. Unfortunately the version you would get at this time would not include the upcoming features that are in Beta. No date has been announced on when that new version will be released. And we also don't know if one purchases the current version which is lacking the additional display output useful for streaming would be able to purchase that update after it is released.
Unfortunately the purchase page no longer lists that option so you would need to call EW by telephone (+1-918-250-1493) to make the purchase.