compatibility for a new cassette and chain
4600 is the previous Shimano Tiagra series (4700 is the current version).
As far as I’m aware all 10 speed cassettes have the same cog spacing, so you should  be able to use any 10 speed cassette and chain. More expensive cassettes are usually lighter and maybe stiffer which makes them shift ever so slightly better. They are a wear part, I wouldn’t spend too much money on them.
Note: The current Tiagra 4700 groupset has different pull ratios for the derailleur and shifter, but that doesn’t affect the cassette spacing.