Hi, I will be on a road trip in a couple months and I will mainly be listening to scanner/cb audio and want to be able to hear communications as best as possible over the car stereo Some am/fm but over all just a radio hobbiest. I am speaking over-ear only, and nothing super expensive. ( $80-ish tops)
I wouldn't waste money on a noise cancelling headphone at that price-range.
I'd get a decent set of IEMs, and maybe buy memory foam tips (Comply is a brand that makes these).
As memory foam tips act like regular ear-plugs and will block out most sound compared to the standard silicone tips that block out less sound.
However, silicone tips last much longer, and are much cheaper to replace, and even with silicone tips most IEMs will block out more sound than many over-ear headphones so you may not need to upgrade the tips at all.
I'd say full-size, closed back, and as cheap as possible!
AM/CB will give you a headache on anything accurate before you get to the end of your street! Try the Sennheiser HD201 for under $30, they'll be fine unless you sit on them - so don't be a breaker breaker!