Burn works great. Thanks for bringing it to my attention! ...and for copy it works just like I remember the MacOS used to work. Am I remembering this incorrectly?
Like some other forum members, I've been using Toast from version 3 to 7 and later on the Burn app. Therefore I can't remember if there ever was a Mac OS X internal burn function to make a direct copy of a CD. As far as I remember, Mac OS X didn't have such an option. The Burn app Icon is quite the same like the former Mac OS X icon for the burn function. Maybe you're remembering right and some version of macOS could manage CD duplication, but I can't tell.
Mp4 is just a container format and can host various codec formats. For backup purposes, I'd recommend a lossless format like WAV (most common for Windows), AIFF (most common for Mac), FLAC (most common open source audio format) or ALAC (Apple Lossless). If you go for ALAC, you could put that into a mp4 container with file extension m4a. It is also common to use m4a for the lossy AAC format, don't mix that up. In Redbook standard the audio format of a CDA is a two-channel signed 16-bit Linear PCM with a sample rate of 44.1 kHz, that you could write e.g. to AIFF, WAV or PCM file. Burn app recommends WAV or FLAC for high quality direct burning of a CDA. To play the audio files from other devices, maybe a smaller lossy file format like mp3, AAC or Ogg Vorbis is more suitable. The right format and setting depends on the storage capacity, the audio player and your demands on quality.
If I hook a thumb drive to my car via USB, will it have the ability to play these tunes, or do I need an interface like an iPod?
I agree with the others. It depends on the player. Many modern players can play mp3 files directly from USB. Some players need a special folder structure on the USB thumb drive. For the older players with no USB port or if your preferred audio format isn't supported, you might need an additional audio player like an iPod.
I’m just curious about recording a bunch of songs, if there is any control in Burn (the app) to set pauses, or it’s just automatic?
In preferences of Burn, you can set-up the length of pauses before every song. It's called pregap time and defaults to 2 seconds.