Went last week and caught a few Sandies, all males; does this mean the creek sandy window is closing? Also are creeks good year round for other species like cats and large mouth? Or just the spring?

You will have some resident species year round in most creeks

They are still there.

I think we still have a solid two weeks.

pretty much any body of water that's not stagnant will hold perch, cats and most will have bass, probably carp as well. they get populated by birds and other ways.

It's really just a matter of how big they are, if you can catch them and how to catch them. I've caught eater sized catfish in creeks less than 10ft across and only a few feet deep.

Cooler weather will keep them in there longer than normal. Caught 10 males in the creek today. I have only caught a handful of females all year.