Does an external drive on PS4 with Sims 4 improve the game?

Not nessecarly your loading time for sims is more based on your packs you have and households you have a hard drive will just give you more space on your console so if you have more than the max sim counter that can slow down your game. The performance of a game doesn't get effected by having other games it's more about what you have on the game that is slow for you so for sims check how many households you have the max sims count is 150 that is on options and game play I think and she how many packs you have also how many saves you have try and keep to the one save since you can have multiple on that save :)