Is it possible make tweaked car in editor? I mean like engine with vtec and can it be saved and upload? Or something else tweks what editor dont support now.

Yes, tweak mods are allowed - in fact they are put into a special "Tweak mods" category. You can filter them in game or on the website by toggling the "Include Tweak Mods" button.

You can only make engine tweaks that are supported by the LFS editor, though. VTEC is not supported.