Don' t mix your brass.
You can use any brand you want, they are just showing you what they used. Just remember to start at least a couple grains below the maximums listed in the books and then stick to the same brand of brass thereafter. If you switch brass you should start over working up your powder charge.

Changing any component of a load will change the performance of the load.
Need to use the same brass, primer, powder, powder charge, and bullet seating depth every time or the velocity or point of impact will change with each component change you make.

If you are shooting max loads this is very important as mixing your brass could result in some dangerous pressures.
At the least you will experience point of impact changes from using different brands of brass, all other components being equal.

If you are shooting groups or trying to sight in with mixed brass lots this will really mess you up.