The 11" will be overkill for the 28qt tubs, even though all I use is 11". LOL
You will need two stats so you might as well order them at the same time.
Where you get them is up to you, I personal like Reptile Basics, and recommend them along with their VE stats.
That is a whole nother story and EVERYONE here is going to start with their thoughts on what you need to buy.
I say get the one that has the features YOU want.