There are others on this site far more knowledgeable then me and I'd love to hear their opinions...
However, I do have a somewhat unique perspective so I'll share what I know...
All done
Just kidding, Some manufactures sell only sets and others split them apart.
Some people say do it some say don't do it.
My thought is that if you have a matched set that is ideal as you have no worries.. You know it will work.
That being said, I have sold many hundreds of mixed sets.
In the last 15 years I have only had one case come back because the customer said it wouldn't fit.
It was promptly sold to another customer and it worked fine.
So, if I had the option for a matched pair that would be my first choice.
But, I would gladly use a mixed set if that was within my budget or that was all I could find.