The start of my rat journey wasn't great, I picked up two shy boys from gumtree.. they were very scared and I was scared so for weeks it wold be them hiding under the wardrobe and me pleading for hours for them to come out. It was only through finding some help via a local rat club they came round slightly and I met other rats and learnt how to handle them, but I noticed the huge difference when I got my first breeder kits. Sadly they just don't get the socialisation and handling in a pet shop, but that isn't to say they can't become absolute cuties! It just means you have to put a bit more work in, and with rats, i'd say the quicker the better.
The reason I said about a smaller cage and not overloading it with things, is you want them to be interested in YOU. You want them to get excited when you come to them, not just for the prospect of food! If they have lots of toys and enrichment you may seem boring in comparisson! So resisting the urge to fully pack out the cage and give them lots of freedom will actually pay off.
My kits haven't had any free range yet (apart from a night of fancy on new Years Eve when I left the cage door open and found them next day behind the sofa!) So I wouldn't worry about that yet. They have been on the sofa but I like them to learn the boundaries early on.. im quite a strict rat mum now! They are currently learning that I dont respond to having my sleeve tugged for attention.. and learnign that the cage edge is dangerous!
I also get them used to having health checks and nails clippedd at this age... it really all does pay off to put the work in as kits because they can be stubborn things and habits stick!
Your main focus now is getting them used to handling and not running away. They will be hyper but you know the difference between excited and scared.
A paper bag maight be too rustly, you want to create a safe, warm space. A old fabric tote bag with some fleece in can work,they are quick to make, you just want a bag like patttern, just a square and sew down 3 sides will do.
Looking forward to following both your progress
Any questions just ask x