Thanks, @dfrazer!
I have never used the YN-560 TX, so I can’t really comment on it, but the YN-560 IV is basically the TX with a flash on the end of it. It’s very handy to be able to adjust the power on the lights remotely! However, I don’t know whether you’ll be able to make individual adjustments to each speedlight, or whether they will all be adjusted at the same time. I’d be happy to test and find out though, if you send me a few of the flashes! 🙂 Seriously though, with a combination of groups and channels, I think there has to be a way to do it.
I would definitely recommend that you buy from an authorized retailer like Adorama or B&H. I already found out that Youngno has some issues with reliability. Youngno has a 1 year warranty on their flash, and it’s worth the peace of mind to know that Adorama will replace them for you if it goes bad with no questions asked.
One more comment: if the flash is your main light source, adjusting your shutter speed will not affect the exposure much because the flash sends all that light out really fast. Adjusting the aperture and ISO will have the normal effect.
You’re right, I guess I forgot to mention that in this post. I remembered having mentioned it before, (obviously in another post though) so I figured I had it all covered, when I didn’t! 🙂