hm, so what does "BoxTrapper" really do in simple words and do you suggest it to be enabled?
Box Trapper is pretty well explained here: 30 Seconds to No More Spam with BoxTrapper | cPanel Blog
Basically, when someone who isn't whitelisted emails you, before you receive the email BoxTrapper sends them a verification email - they have to click a link within it to prove they're actually human and they sent the message. If they don't reply the mail stays in the BoxTrapper review queue where you can manually review the mail. Mail that you approve or mail that becomes verified will automatically be accepted by BoxTrapper for future deliveries and anyone you send mail to will be whitelisted automatically.
As far as if I suggest it to be enabled, that really depends on the mailbox and the user. If the box receives a lot of automated mail, or mail from unknown senders then no, probably I would not suggest it. But if it's a personal email address and you're really only expecting mail from senders you know - for sure, this is a great way to combat spam or unwanted email.
And regarding "Spam Box Delivery" - so regardless checkbox state at the account creation screen - if it is disabled in Tweak settings - it will also be disabled for the account, right?
Exactly, that's what I saw in my testing.