I don't want to purpose a paid subscription for the moment may be later.

CB Paid Subscriptions is primarily a subscription management plugin. It however does have Merchandise plans which might be of help. You could also create 1 lifetime subscription per ebook or video then use all the subscription features to grant accessed to whatever content you need to grant access to. Your alternative is to look into other e-commerce extensions available for Joomla, but given your needs are strictly digital CBSubs should be able to handle it fine.

allow them to put a comment on my articles.

CB Activity can provide article commenting.

I would like to change the appearance of the registration page, and removes the messages and the background photo, I mean personalize this page.

That's just built into core free CB. Change what fields are available within CB > Field Management. You can create tabs in CB > Tab Management to organize your fields. You can also use the new layout features shown below to 100% customize CB to look like whatever you need with custom HTML and CSS.

www.joomlapolis.com/blog/kyle/19009-profile-layouts

Recommend trying out our demo site below. Full backend and frontend access is provided and it resets automatically so feel free to tinker around with it as long as you need.

demo.cbdemosites.com/

Note have moved your topic to Presales for more visibility.

For CB activity, I use joomlack pagebuilder for my article, is it gonna work with this on joomla 3 ?

The integration included in CB Activity is built for Joomla articles. As long as they are Joomla articles and call Joomla article events it should work otherwise no you'd need a custom solution, which is likely doable with CB Auto Actions depending on what pagebuilder API is available. You may need to look into exclusively pagebuilder solutions though. I personally don't recommend using anything other than Joomla articles for articles as you significantly limit yourself in regards to what extensions you can use (there are A LOT for Joomla articles).

So if I understand well I can buy CB activity and CB subscription?

Yes, if that's what you feel you need. I suggest giving them a try on our demo site to get an idea of how they'll work.

CB Activity Joomla Article Demo
demo.cbdemosites.com/login-as/user?demo=926

CB Paid Subscriptions Demo
demo.cbdemosites.com/demos/cb-paid-subscriptions/plans

If I pay 99 USD for each for 3 months, I can use them later than 3 months right?

Yes, all products can be used after your subscription expires but they may become unstable due to missing fixes should a bug arise. However the Professional subscription does not include CB Paid Subscriptions. You need a Developer subscription or to purchase CB Paid Subscriptions individually. Note you can build a custom package from the below page and only buy those 2 addons if so desired (see custom bundle link at the top).

www.joomlapolis.com/addons

Is the builder pack include all the plugins? Do you recommend me this one ?

CB Package Builder? That's available standalone or as part of the Developer subscription. It's basically an advanced download manager. I don't recommend it unless you need a download manager. It powers our downloads page below.

www.joomlapolis.com/downloads

It is also automating all of our product pages like the following.

www.joomlapolis.com/community-builder