suggestions to a potential new rat parent?

there are two very sweet males at a local pet store my partner and I are extremely interested in, we held off on the impulse purchase because we have little idea on how to care for them. we do intend on getting them both.
i did a little digging on this subreddit and pulled out a cage that someone suggested works well, and now i just wonder about bedding and cage setup+toys and intentional decoration. (links or local pet store brands that are safe/good pls?)
my partner and i currently have 4 fish tanks, a regal jumping spider, and a tarantula in our care, so making the leap to rats is a little different.
the rats we are looking at are about a month old (the worker said) and appear to be very clingy and social and okay with human interaction, so how often should they be handled, let wander, left alone, how are they with fish and bugs? lol.
just general stuff from whoever wants to give advice. i do know a few things about rats in general, but not anything on how to keep them.