Grammar is like training wheels. If/when you do become fluent you won't need grammar because comprehension will have become reflexive and speaking largely automatic. The rules your brain uses to interpret messages become hardwired into the brain. Your brain will be reconfigured. This reconfiguration of the brain is not the same as knowing a description of a bunch of grammar points. In fact 'knowing' the grammar rules in this way is not necessarily even a required step in the brain reconfiguration. That said, grammar rules can be helpful sometimes in interpreting messages that your brain is not yet able to understand intuitively (text in particular). I'd recommend studying grammar as a means if and when it is strictly necessary, not as an end in itself. Regularly read/listen/speak japanese and when something pops up that you don't understand, look it up online. Give yourself a rough overview of grammar with something like taekim and refer back to it when necessary. Don't expect to remember or understand everything. You could memorize all the grammar in some grammar reference or textbook, but until your brain starts reconfiguring itself via practice you won't be able to intuitively comprehend text or speech (decode maybe).
No beginner textbook is going to cover enough to make native materials easily comprehensible. And grammar dictionaries are made redundant by internet search engines. Just pick a beginner resource (any of them) and read through it taking from it what you will. Then get stuck into using native materials.
I sometimes wonder if intuitive comprehension is more effectively trained in the absence of any grammar crutches. Think about it, if you're reading along and something triggers a grammar description, then at that point your brain performs a translation and stops wondering (based on the surrounding words and context alone) what the meaning is.
No beginner textbook is going to cover enough to make native materials easily comprehensible. And grammar dictionaries are made redundant by internet search engines. Just pick a beginner resource (any of them) and read through it taking from it what you will. Then get stuck into using native materials.
I sometimes wonder if intuitive comprehension is more effectively trained in the absence of any grammar crutches. Think about it, if you're reading along and something triggers a grammar description, then at that point your brain performs a translation and stops wondering (based on the surrounding words and context alone) what the meaning is.

The grammar/training wheels analogy seems apt. As you mention it's possible to learn how to