You should be able to install on/boot from a USB stick, but you may notice some slowdown compared to running on internal storage. OK for evaluating, maybe OK for long-term use if the slowdown doesn’t bother you or is unnoticable.
Personally, I’ve been using MX-Linux (KDE) on an Acer Chromebook CB317 with 4GB RAM and 64GB storage, for a couple years, daily. Looks like MX says 6GB storage is required. But depending on what you want to use it for, you will quickly run out of space on a 16GB disk (with any OS, of course.)
If you are evaluating distros, Ventoy may be very useful. It lets you take a large(ish) USB stick and drop multiple isos on it, then boot from the stick and choose an iso to “really boot” from.
A few notes on “light Linux distros” and low-spec hardware…
If you plan to use a browser a lot, especially for YouTube or other video streaming, “light linux” will not help if the CPU/video card can’t keep up with decoding/displaying video. Not an issue for yours, probably, but on some fairly old laptops I’ve tried (not chromebooks,) YouTube is a slide show, despite the system running well otherwise. On my CB317 it’s fine. Probably yours too, but I’m just mentioning this for completeness.
You have 4GB soldered RAM, right?
If you open many tabs in a web browser, you may run out of memory. Stay on top of it, check free ram/swap frequently, close tabs and/or restart the browser before it becomes a problem.
Personally, I’m using zram swap with a factor of 150% (long story but yes you can set it higher than 100% physical ram,) and Brave set to suspend inactive tabs after 5 minutes. If I don’t pay attention I can end up over 100 tabs open, but then I’d better close about half of them, and/or restart the browser. I have had the machine “lock up” a few times (churning swap I think) when I wasn’t paying attention.