Well, I have access to MANY different TSCs starting w/i 15 miles from me.  Two of the TSCs actually have some chicken knowledgeable  employees IF they are working when i am there (since their hours are on a revolving status - it changes daily as to who is where when).  My hours are 0700 - 1730, then I have drive time.  I have appointments & commitments on Fridays/Saturdays into the afternoon hours.  So my visit times are very limited and I actually often miss them completely because they close before I can get to them...
That said.  Each of the TSCs that I've gone to is in different counties and they all use a different hatchery to get their chicks (from what i've been able to determine).  I've never seen a great selection of chicks & considering I have a feed store that not only has hours that I can get to (& will be open if I call and say I'm on my way, but will be there @ such & such time after closing - I've been a customer with them for more than 15 years and currently spend 100s of $$/month with them), but they can special order specific breeds and get them in every week with theirs and will keep them 'till I can get there.  MUCHO better.  Also, the feed store now carries different breeds every week and has them most of the year, not just during "Chick month" like 
TSC.
Our TSCs used to allow customers access to the chicks and it never failed - chicks were put down/back into the wrong brooder(s).  So YES, mixed breeds all together.  Most employees didn't know the difference - shoot - as many different chickens as I've now had and have seen at shows/breeder farms, I can't tell the differences between chicks.  Then, YES, there also appear to be some who just DON"T CARE - they have a lot of mixed duties that take them all over "their stores" and no-one at NCs seems to work in any one area.  This year, each of the TSCs I visited put up tall fencing around their brooder set ups and locked the gates.  Just getting an employee to come to the pen to look at chicks you couldn't see from outside of the pens was difficult (I only went to the 3 closest TSCs this year, not the 5 or 6 as in past years) - but it WAS safer for the chicks and there was LESS mixing.  If the person who ordered the chicks was good enough to get breeds that were different colors, then it was that much easier.  Some didn't even have that, though.
Because the chicks all seem to come from different hatcheries, I've been able to observe the chicks over the last 8 years.  Some hatcheries have a BIG PROBLEM with chick type coming close to an actual breed SOP and with chick health/thrifty-ness.  Sad thing is, I couldn't match the hatcheries - because most peeps at 
TSC, again, don't know which hatchery they are dealing with.  The ordering managers aren't usually there when I'm there - late eves or late afternoon Sat or Sundays.  I still don't know which hatcheries each 
TSC uses, but there are marked differences in chicks so feel confident saying they use different hatcheries.
Beccazon - you are in a state that has quite a few breeders of chickens, show access and Heritage chicken breeders.  If you think you like a certain breed, I would certainly look into going that route.  Also, not every chicken hatched, even by experienced, long time breeders, will come close to matching the breeds actual SOP.  The goal is to get most of your stock coming close - and it is tricky achieving that.  Then there are also different goals (for some breeds) w/i each breed SOP...
and be careful with the "reputable" hatchery statement.  I've had mislabeled chicks that didn't come close to matching SOPs from several hatcheries now.  I've also gotten the same from "breeders" - even NPIP breeders.  I've been trying to figure out how those stay in business, but then again, like a hatchery, I've now dealt with several breeders that don't improve their own stock - just hatch lots of eggs to sell.  THAT is much more frustrating than getting mislabeled stock from a hatchery, IMO - especially since the cost is significantly higher!
I've made other people upset that have wanted to purchase some of my eggs/from my culled breeding stock - but I've not hit the resulting birds that I want to market to anyone else yet "as mine"...
I've learned a lot over the years and I seem to learn more each day/week/month/year.  I've enjoyed the stock I've gotten and I'm now trying to only get from breeders that I've managed to dig through and find out that they are improving their own stock (not just 1 or 2 parents popping out chicks that are all sold).  I'm also trying to learn how to incubate my own now - yikes - serious learning curve.  Right now, I'm in the mind set "how does ANYONE ever do this"...  
Since my family has been horse breeders and I've bred Shetlands since 1995, I know how difficult it can be to get that elusive BEST specimen.  It takes time, it takes resources, it takes learning to cull in some way.  Even breeding best to best usually doesn't lead to best or more improved offspring.  Not easy and not for the faint of heart - even with chickens (which can legally & yumily end up in the freezer when you cull).  I've seen a lot of breeds (different animals - livestock and pets) over the last 30 years CHANGE a lot and not all for the better.  I think it's great seeing Heritage breeders get started and really work to better their special breed and for those that work with more than one - WOW - I commend them...  
I actually got my biggest start in chickens with 
TSC after being given 15 mixed bantam hatchery chicks at Christmas 2010...  Of the first several purchases, not all made it/survived and can't say it was my lack of care.  A few never laid - though they were definitely pullets...  I can say that I never got roosters with my pullet purchases the first couple of years.  That was a god-send!  LOL.  The pullets that I got all seemed to be what they were supposed to be - but WHOO were there differences in color/shades & even type , again LOL.  
My "heartbreak" started when I started looking for specific breeds from "breeders"...