Are they fancy goldfish or regular ones like comets, shubs or commons?
I scratched the species of that will be eaten by non-fantail goldfish, aren't suited to unheated tanks, or both.
Corys are a risk with bigger goldfish, but in a 200L you should be fine.
I would go with peppered corys, not albino/bronze - which are tropical species IMO, they would prefer a heater in their tank to at least bring it up to 23-24*C (fishbase and wikipedia actually list 25*C as the natural temperature).
Cherry barbs are more tropical too...they would need a heater, non-fantail goldfish would eat them as well.
You could add a heater with the goldfish if you wanted...but speeding up their metabolism would mean you would have to add a lot of other equipment to keep the water clean and oxygenated for these big, messy and oxygen demanding fish - like a vastly over rated external, and a spraybar splashing at the surface or a big airpump.
Hillstream loaches aren't suitable simply because they require different conditions to goldfish (better water conditions, faster water flow) and they don't compete well for food at all with them. They seldom last longer than a few months with goldfish.
Options for keeping with comets/shubs/commons would be Buenos Aires tetras and rosy barbs, as well as rosy red minnows.
If they are fantails of some sort, then the danios/tetras will be perfectly fine. Bigger Amano shrimp would be suitable too, as well as variatus platies (normal platys should be fine tbh, they are usually hybrids you find in stores).
Good to see your giving the goldfish more room, they are fun fish to keep if you like big eating/pooping machines

. They will grow fast and you can always find them a garden pond in summer if you want to focus on other fish.