1. I don't want to show plan options in registration page. Is it possible to auto-subscribe users to a plan once they complete the registration process?
You'll need to set a free or paid plan as Default, Exclusive, and display on registration. Once done you can hide the CBSubs plans using the below CSS. Aside from this method there's no other way to give them a subscription on registration and plans be hidden at same time.
Code:
.cbRegistration #cbfr_cbregplans {
display: none;
}
2. I have a free membership plan for a certain category people. Even though it is free, I would still like to approve their subscription before it goes live. Is that possible. The only control seems to be in the registration workflow, but I want to separate subscription from registration.
There is no subscription approval. There's only registration approval. Perhaps setting that plan to require admin approval before or after payment would be acceptable (either/or is fine as plan is active immediately as it's a free plan). This can be configured on the Workflows tab of your plan.