in house will probably have a lit team and a corporate team. the corporate team will handle the M&A, securities, licensing, etc. matters. I'm not sure how much say they have on the direction of the company, this is probably something left up to Management. it really depends on the size of the legal dept of the company. Some companies like Cisco's or Google's are pretty much like a law firm with its own small practice groups. On the other hand, smaller tech companies and start-ups will have a small team overseeing everything and have more responsibility.
No. Few companies have legal depts that big outside of the insurance industry. They retain BigLaw firms and their legal team farms stuff out to them. As for tax, I don't know of many companies with in-house tax lawyers. They wouldn't have enough work. Plus, their auditors are required to be independent companies and their tax lawyers may need to be as well unless they want to carry their own insurance.