The more important first impressions to leave a VC with are:
1) That you both are credible and inspire confidence that you can execute the plan you're fundraising on.
2) That there is good chemistry and a great relationship between the two of you;
3) That you can adequately address the concerns/objections/questions the VC raises.

The CEO is expected to do most of the talking because the CEO should be the best person in the company at articulating the vision and value of the product and company you're building.

If your CTO is comfortable presenting part of the pitch, it would be ideal for the CTO to speak to the product slides. The most important thing is for the CTO not to be a "bump on the log" meaning that you don't want them sitting there for most of the presentation with nothing to say. If you feel that's the case, you really shouldn't bring your CTO. Most VC meetings will not get technical and under the hood.

Each question answered should be answered by the person best qualified to speak to that question. You should make eye-contact with your partner and use subtle body language to find a way to cue the other person to speak to that question or simply offer "CTO, would you like to answer that?"

Bottom line, make sure that the CTO can speak confidently enough about the product and vision, otherwise -unless specifically asked by the VC - come alone.

Fundraising is a big distraction to building and a good VC will always respect that in a first meeting, the CTO can be excused from attending in priority of building product.

Happy to talk to you both on a call about helping get you feeling a bit more confident and prepared before your meeting. I was formerly a VC associate for a $500m fund and have raised money from VCs as a serial entrepreneur.