It's hard to really explain what to do with your voice to be high-energy without sounding too nervous (i.e. talking too fast). Your best bet is to model yourself after someone who does appear high-energy but still comfortable and high-value. The best example I can think of is Mehow. Right here (
YouTube - Mehow INFIELD EXPOSED - "Party Girl (narrated)" - 1/2 )a random YouTube video I found of him both in-set and out of set explaining what's going on. In both cases, his voice is high-energy. He gives off this fun kind of positive energy vibe that is very attractive. However, he also conveys focus with his voice. A very well documented and almost universally recommended way of doing this is by pausing often and for different lengths of time. It makes... everything you say... very... very... interesting. Combine effective pausing with a dynamic voice the way Mehow does, but also play to your own voice. Every mPUA employs similar combinations of elements to create a high-energy but comfortable voice tone, but I chose Mehow because I think his energy is more embellished than others. You can really see what I mean by "dynamic voice" in this video, where nothing he says is in the least bit monotone. That's what you need to sound high-energy, use pauses to make what you're saying more interesting and also to appear more comfortable. Add that with what you already know (i.e. slowing down your talking a little bit) and you'll do fine. Listen to many mPUAs speak, especially in-set. You can pick up little nuances that you can model after them to create your own style, in addition to the largely universal stuff above.