I will try my best to answer here.

What official plan this deal is comparable to.

Since its a customized lifetime deal exclusively for app-sumo, nothing on the public pricing page https://socialbook.io/plans?plugin=1 matches this plan. But you can still refer to the Pro plan there. And Yes ,you will receive all future product upgrade for the Pro plan for free!

What’s the difference between SocialBook Builder and other tools (TubeBuddy, VidIQ, etc)
I wrote a detailed comparison between SocialBook builder and VidIQ before: You can check it out here:
https://medium.com/@chen_9548/5-reasons-why-you-should-switch-from-vidiq-to-socialbook-builder-4cea05226597

I found that many sumo-lings are super techy! (like me:) So I would like to stress one point that many non-techy people would probably won’t notice:

All of the YouTube tools on the market requires really scary permissions:
https://miro.medium.com/max/816/0*CvkIKwooih6D-oPD but SocialBook would only ask for two simple read-only permission when you sign up. Why do people need to give away control of their channels just because they need to see some tag recommendation?

And SocialBook has many unique features that none of the tools outside provide. The one we are really proud of is the Thumbnail Maker. It allows you to extract a frame from a video, and then extract your person image out of the thumbnail.

Also we pride ourselves in data analytics. The stats we provide for each channel https://socialbook.io/demo/AzzyLand-614958 are the best in the market.

Is channel changeable?
Yes, you can always disconnect your current channel, and switch to another one. All your data will remain there.