Not to mention GPU support, HDR support, now 8k support, color grading, LUT support, hardware decoding support, 360 degree video support, 3D video support, storyboarding, timeline nesting, motion tracking, image stabilization, warp flow, optical flow slow motion, I could go on and on...
But first, READ THE SYSTEM REQUIREMENTS, as they have gone up a good bit since Vegas 8, then try the demo before you buy.
Wasn't 8.1 the first 64-bit version of Vegas? LOL...
Version 17 has motion tracking, decent built-in stabilization, improved Nvidia & AMD GPU encoding/decoding, HDR color support, nested timelines (good for keeping preview compilation clips of existing projects updated), etc...
As far as the suite, go to the Boris website & see if you need those add-ons. If you only have 8.1, and author/burn playable DVDs or Blu-rays, then the updated DVD Architect is worth the price-difference... I still have clients that want a DVD / Blu-ray to play a training video on an old break-room TV/DVD player combo, etc. so it is handy to have... If you use the right template in Vegas, DVD Architect doesn't need to re-render the video & it will keep all of your chapter markers from the timeline...
I've been using Vegas since 3.0 & my favorite/stable releases were 10e, 12 & 15... Those 3 rarely crash so sometimes I start a complex/lengthy client project on an earlier version of Vegas, do all of my cuts & splices & color editing before loading the mostly completed project into a later version for better GPU-assisted rendering, etc.
The only difference between Vegas Pro and Vegas Pro Edit is the license for DVD Architect. If you don't author DVDs or Blu-ray discs Vegas Pro Edit is fine.
Try Options/Preferences/Audio Device and at the first field (Audio Device Type) check to make sure that the device selection is appropriate to your system. If you are using the bog standard audio of your computer, Microsoft Sound Mapper or Windows Classic Driver should work, but if your computer's audio is directed through another audio device like a sound card or an external audio interface, then the audio device selected in Vegas Pro wou;d likely need to be that audio device/interface.
Also, check that track header as well as Master and Preview Bus settings (the latter 2 in the Mixing Console) aren't muted.