Well the differences are that Cakes is generally more modular, so you don't have to update the whole firmware to update parts of it or add a new feature to it
There's 10.4 firm which is currently only supported by nightlies (which aren't stable) and 10.3 uses 10.2's firm, so if you want a stable experience then use the 10.2 firm (to be clear you can still update to 10.5 with it) OP doesn't have a guide for it but it isn't hard (just place the files where they need to go, enable the correct patches and go from there)
you can keep all of your CIAs, they're installed on the SD card so they're safe
Is there a spoofer I can use for now to spoof 10.2 to 10.5? Thanks for all of your help.