To better grappling, you need to grapple. To better striking, you need to strike. It's really that simple. Being a well rounded martial artist is a different story.

You should never be "muscling" anything in the martial arts. Once you starting muscling it, you've completely abandoned technique and technical principles. Skill is what the martial arts is about, not bulk, brawn or physical force in general. You should review your fundamentals and go back through them step by step.

No its rather poor grappling technique if you are worried too much about strength that you have to get so big that you cannot learn striking as well.

And vice-versa? When i practice wrestling or grappling its more muscle strength and lifting opponent, and boxing and kicking is opposite, less muscle mass and more flexbility, like wrestling requiers bulkiness and striking requieres slim and lean body.