For me, the biggest benefit is not putting hormones in my body. And not needing to use a barrier every single time (I have a lot of skin issues and suffer from contact dermatitis and/or UTIs from latex condoms (we've since switched to non-latex condoms). I love knowing where I am in my cycle and seeing that my body is doing what it is supposed to be doing. It's also economical - no money out for pills or anything like that.
Been using FAM for about a year and absolutely love it.
thick, white CM is what you would normally call "creamy" and is not quite as fertile as that clear stringy "stretchy" CM, which is what we call egg-white cervical mucus or EWCM- that's exactly what it looks like. This is your most fertile mucus and you should be able to stretch it a few inches before it breaks. Typically, you'll see this for a couple days before you O and maybe a day after, but most women dry up pretty quick after ovulation.
As for arousal fluid- it tends to dry up pretty quick and absorbs/dries more readily that fertile CM. On a finger it might dry up where CM will glisten and stick around. Same with toilet paper- if it soaks in, I tend to think arousal fluid. Also just knowing what you've been doing - if you are feeling a little "excited" or have been intimate in the past couple of hours, it's probably arousal fluid. If you've been doing unpleasant tasks or busy with work and not thinking about sex and you have some CM, it's probably safe to assume that it's CM. Of course, your signature makes me think that you are younger than me and I was definitely more "excitable" 10 years ago than I am now (at 32) so it might be easier for me to tell on that.
Definitely read Taking Charge of Your Fertility and I would recommend doing the little class series on fertility friend's website. Very informative.