Can someone give me an idea or picture of how a 18x9.75 +20 offset would look like or how far it'll stick out?

 

I'm guessing you're talking about the back... Basically 33et 9.5" is even with the fender, so 20et will stick out 13mm more than that and an extra 1/4 inch means an extra 1/8" out on each side which is just over 3mm. So basically it will stick out around 16mm further than flush, which is a little more than half an inch (12.7mm).