I am with the Orthodox Presbyterian Church, which is very Calvinist, and according to my pastor, if it's not expressly forbidden in scripture then the church can't forbid it and if it's not expressly commanded of us in scripture then the church can't command it of us. I chew tobacco and another guy smokes and pastor told me that that is Christian liberty. He's pretty knowledgeable to. He has an MDiv from Westminster seminary and I trust what he says. Also, we have some guys in our church that enjoy beer and scotch but they don't abuse it. The Bible just says not to be drunk. As for being involved in the world, it depends on the tradition within Calvinism. In our church there's a heavy influence from Calvin, Bavinck, Vos, and Kuyper, and all of these think we need to engage the world and participate fully. Calvinism usually recognizes a strict separation between civil and ecclesiastical government, that the two should not overlap. For example, the government shouldn't dictate style of worship in the church or what denomination you can belong to and the church shouldn't dictate the speed limit. However, as an individual you have every right and are encouraged to participate in the civil process. Bavinck has a small book called Christian worldview where he articulates this, although It's not an easy read. You could go directly to the horses mouth and read Calvin's institutes. It has a section on civil government. So does the Westminster confession of faith.