The ability to customize the player characters with a variety of clothing has returned in Grand Theft Auto V. It has been improved, allowing the player to choose from a diverse and a larger variety of clothes.
You can tell that the protagonist does not like the clothing the player wants to buy for him/her by the way he/she moves around when going through the list of clothes.
Despite being able to buy numerous pairs of shoes for Michael and Trevor, you cannot cycle through footwear you have purchased in their respective safehouses, the only place you can actually choose shoes is in stores. This is most likely a developer oversight.
Some sets use clothes derived from other sets. For example, Michael's Swimsuit and Assault sets will form the Commando set.
On a lot of the caps that you can purchase for Franklin, if you look closely at the back you can see an OG logo, and writing saying 'Old Gen'. This is likely a parody of the real world hat manufacturer New Era, which are known for their huge variety of Snapbacks and other types of hats.