So I have a Tekin RX8 Gen2 esc that I've been using and recently purchased a Savox SW-1211SG servo to replace a Arrma ADS-15M servo that I just threw in my old Associated RC8TE to get it going. Anyways, my question is...Does my Tekin RX8 Gen2 esc switch the servo voltage automatically to 7.4v or do I have to change it? I just want to get the most out of that Savox servo. Hopefully someone can help me out.

It does not, you have to change it.

Do you happen to know how to? Hopefully it doesn't require the Tekin Hotwire cause I don't own one...

No but there's a good chance you'll need one. Check the manual for that ESC.

Hotwire only.

Wish they defaulted to 8.4v. I don't have anything that cant handle it.

That would be a bad idea because if someone buys a 6 volt servo, plugs it in, and powers it up; the servo goes up in smoke and you'll see posts like 'avoid X servo brand!' or 'avoid Tekin ESC's!'

But to answer the OP's question, you'll need hotwire to change the parameters.