There is a great variation in land here in TN. We have everything from wide open beanfields to mountainous terrain where you can see for miles. Bottomland choked with briars and honeysuckle to cut over forest on large timber company tracts that you can barely see 10 feet in front of you, much less find a shooting lane. If your cousin says 100 yards is the usual shot, I think as long as your comfortable with the 45-70 it should be ok. It would be alot better than using something you were unfamiliar with. I think the key would be to practice at several different ranges to be prepared. There is several public hunting opportunities here, and you might even get invited to another piece of property that is vastly different. The TVA has high power lines running all over the countryside, so you never know when you might run into a piece of property that is really thick with a wide clearcut through the middle of it for the high power lines. Likewise you may hunt a big beanfield where the only way you can get a jump on the deer is to get into a small patch of woods where they congregate.
Depending on the time you come, I think I would tell you to bring your muzzleloader too! It opens up more time and opportunity here, although you need a separate tag for muzzleloader. Talk to your cousin, he will tell you all about it.
Here are a few examples of what you can expect. The first three (only first two are mine) are from North West TN. The last one is from federal government land that is open to the public on a limited basis.
