Faulty disks

I have multiple G Speeds (48TB) and have a few disks which needs to be replaced. The replacement drives (8TB) are €300 more expensive with cradle then without (also availability is an issue). Can I replace the faulty drives with other ones or do they need to be exactly the same?

In other words if I buy the same drives without the cradle, can I use them?

And can I use other type of drives, but with same capacity?

I use them in RAID 5

Yes you can purchase them without the cradle and just swap them. The cradles just unscrew from the drive.

You want to make sure you replace them with identical drives. Each drive will have a PN on it, make sure you source out those.