Ijust finished N4 deck. I will do at least week without any grammar to solidify n4 deck but what is best course of action afterwards? Continue with n3 deck? Or use a book [I have multiple to choose from including tobira, bunka chuukyuu nihongo etc) and use bunpro as explanation for grammar points and renshuu?
N3 is good There is a lot of essential grammar there. I would not specialise too much and diversify the learning with different resources, so for example do Bunpro regularly for adding new grammar and doing reviews, but also find a book and reading material to follow. Tobira is pretty good, it contains some longer text segments that will probably be challenging at first, but rewarding after a while. Looking up the grammar for each chapter at Bunpro really helps.
Continue with N3 grammar?
If you have the books, use them and add the grammar points manually in Bunpro as you go through the books. It could be a good idea for a bit to concentrate on building up your vocabulary ( here and / or on Renshuu etc ) and then focus again more on Grammar. Just to change things up a bit.
Maybe a bit challenging. Try from time to time to read shounen manga / shoujo manga. On Bookwalker website you can basically read some manga a for free for a limited time (just press on the book cover). Eg:
3a8082e126