I have a "4 rack"... sometimes if I'm doing a "kik in" and a "kik out" mic I'll run the "kik in" [and/or the "kik out"] signal through an IBP
... same with bass mic and DI... and sometimes composite bass signal vs. composite kik signal to get them to work and play well together... but as far as overheads, H/H's and snares go... make sure your kit still sounds like the drum kit when you hit the "mono" button and you'll not require an IBP
in those applications.
FWIW... I have 3x IBP Jr. and 1x IBP in my rack... the IBP is often used for "re-amping" and the IBP Jr's cost less than the IBP and I've never had to 'reamp' more than one thing at a time.
I've also found the IBP's to do some very interesting shit to guitar / vocal relationships... which is another reason there are 4 in my rack [which could turn into 8 in the not too distant future as I'm finding more and more uses for them].
FWIW, I do NOT
add them while tracking except in very rare occasions.
Best of luck with it.