I don't think they are symbolic, unless in some very subtle way that escapes me. A number of names in the novel seem to be coded and there are also several nicknames, so it would appear that Harper Lee did put some thought into naming her characters, as indeed any good writer would. For example, there are bird references in the title of the novel and also in the names Finch and Robinson. Atticus is a very odd name - we are never told if it's his given name or a nickname - and actually means 'from Attica' or 'Athenian'. It may refer to the name which the great Roman lawyer and orator Cicero used for his chief correspondent in his letters and may thus be a loose legal reference to Atticus' profession in the novel. Scout isn't a bad nickname for a very inquisitive little girl. It is hard to see any symbolism in the names you mention, though Link may be an abbreviation of Lincoln, with obvious connotations. Mrs Henry Lafayette Dubose is presumably meant to evoke southern American-French gentility, the middle name referring to the general of the Revolution and the Dubose probably a corruption of the French name Dubois. Mrs Dubose is the great snob of the novel and her sonorous full title certainly emphasises this.