Yes the 5 way does CYA. However I will say with a seasonal pool that gets drained and refilled every year you shouldn't need to test CYA. One of the reasons I bought the TF100 kit was I wanted to play around with the CYA test. I found it to be very subjective and hard to read accurately. Also CYA just needs to be "in the ballpark". So in the end I didn't really find that test useful, and will continue with the following method.
You are going to want to switch to bleach for your chlorine source. When I fill my pool, I add the proper amount of CYA / stabilizer to get to 40ppm by putting in a sock and hanging over the side a few days, give it a squeeze every now and then. I'm confident that is going to get me close enough to 40ppm I don't feel the need to check it with a subjective test. I typically have to back wash at the most twice a year. When I do my first backwash and refill I add a bit more stabilizer to cover that and top off what's been splashed out. I usually go thru some math to come up with what I think is an accurate guestimate, but roughly around 15% of what I put in originally. That's fine enough for me to get back into that 40ppm ballpark for the rest of the summer. Drain at the end of the year and do it again next year. Of course once I shift over to a pool that stays up year round and only gets a partial drain and refill every year the CYA test will come back into play.
With a seasonal pool if you're on top of things from the beginning you can get by with a 5 way at the most. If you already have an algae problem you need to clear up, it would be best to skip straight to the TF-100 to get the proper measurements to clear it up.
There is a CYA - Chlorine chart that will give you the proper corresponding levels. You will find that at 40ppm CYA your minimum chlorine level is 3ppm, 5ppm is your target, I don't remember the shock level. Basically that means you always want to stay above 3ppm chlorine. Theoretically if you shoot for 5ppm when you add you should be down to about 3ppm the next day when you add. You may find there are days or times when your pool uses a bit more or less chlorine per day. You'll get a feel for it, it's ok to shoot a bit over 5ppm when you find your going thru a bit more that 2ppm per day. I run my chlorine a bit high cause I never know if there are going to be 1 or 2 people in the pool during the day or 10. I'd rather be a bit over than under. Going thru too much chlorine can also be an indication of an algae problem. However you can be confident if you're starting from an algae free point, and you've kept up your maintenance, algae should never start.
