How to have it so - When a user checks checkbox for subscribing to a topic, they should not need to confirm this in email? As of now when users check the box after that they receive an email asking them to confirm that if they really want to subscribe.
There is an option in wpForo settings to disable that (settings/features/Enable Subscription Confirmation).
I hope i understood the question correctly.
Please navigate to the Dashboard > Forums >Settings > Features admin page find and enable the "Enable Subscription Confirmation" option, in case if you want to receive the subscription confirmation email, and vice versa, disable if you don't want to receive the confirmation email.