New to the investing world

I'm 27. No debt. Just got into investing. I'm educating myself and I'm very much of a novice when it comes to this. I opened up a ROTH IRA with Fidelity & initially went with FDKVX after speaking with Fidelity advisor. Dug a little deeper and exchanged it for FDKLX (2060) mainly due to the lower expense ratio. However I'm now contemplating exchanging it for FXAIX. I only have about 3k worth at the moment. Would it be wise to exchange the FDKLX for FXAIX for optimal returns or is there another route I should consider taking?

I also have a 401k through my employer (with Fidelity) and currently holding VTTSX. Any advice on that would also be greatly appreciated.

Thank you!