MOC creative process

Hi guys, I bought my first Lego technic after years of not building Legos. I’ve fallen in love with it again and I’d like to attempt some Moc trucks. I’m wondering what that process looks like, is it best to start from the axles and work out like most builds, or is it better to get body lines and incorporate them together? Are the cars truly 1:8? Or is that more of a rough sizing? Any recommendations or tips and tricks would be great, and any YouTube videos you guys know or anything would be...