Is there an overlap with signs if you're on the cusp?

Definitely. There is a 5 day period before and after the change of signs when you are considered on the cusp. The degree of your sign also contributes HOW much of that sign you will tend to show. For example, if youre on the aries/taurus cusp but only have 10 degrees in Taurus, you will exhibit significantly less “taurean” qualities as someone who is 60 degrees in Taurus.

But being on a cusp, you may have significant characteristics of either signs.

However, more important than just your sun sign is your natal chart in general:

all of the planet locations at time of birth play a role on your individual personality, hence why not every sagittarius or every virgo is exactly the same.

The location of your planets and your houses impact things such as your drive (the sign located in Mars), how you express yourself (sign located in Mercury), how you are in relationships (the sign located in Venus), where you find security (the sign located in your Moon)

and so on.

You can do your natal chart for free on several websites. Essentially all you need is your birthdate and time of birth.

www.astro.com is good one :)