Aaahh, bourbon, don't get me started (off topic) - I'll save how I made the acquaintance of Jim and Jack in Chicago 1989, for maybe your Intro Thread.
4 GB is fine for running most Linux Distros.
How large is the USB stick, eg 8 GB, 16 GB? And is it USB 2.0 or 3.0 do you know?
Suggest you start a Bookmark folder in your Browser for Linux matters, because we will give you a lot of reading to do, saves us reinventing the wheel by talking you through a lot of stuff.
There is a concept called Persistence we have in Linux. It involves modifying a USB stick so that changes made can be preserved over reboots when using a Live Distro, or you could do a full install to the stick if it is 16 GB or more.
also mentioned above, Ventoy, which not only allows you to place several Linux .iso files on the one stick, but also to provide Persistence to one of them.
One of our writers has an article on Ventoy here
and I would suggest you read it, and also the comments from Andy following. Andy is our resident expert on Ventoy. He and his wife moved from the UK to Ghana, Africa recently, so just allow for timezone differences.
Two more references, and then you may be full to the brim
DistroWatch is a good site for checking all sorts of things Linux, you can find Nitrux there, and check their Page Hit Ranking in the header for an idea on most used Linux.
Wikipedia have the following for lightweight Linux
and the Linux family in more detail
OK I lied, that was 3 references.
Don't expect to get through it all in a hurry, we're talking about the most diverse operating system you've ever thought of, put together and maintained by hundreds of thousands of users, not just one corporation.
I don't expect we will need to dumb down for you (much), we were all in your shoes at one time or another.
There are no dumb questions, only the ones not asked.
Patience ... is our middle name.