I want to mention that there are also models with 8GB of RAM and more options to choose from in the price range between $350 to $1500.
I am in the market for a Chromebook. This will be a second machine, like a Kindle Fire with a keyboard. I'm not imagining any kind of power use at all, just streaming, reading, word processing, surfing, and monitoring of videos and photos as I shoot them. But that's not to say that I couldn't discover that I like using it for other things too.
Kindle Fire with keyboard, that pretty much is how I use my Asus C302 and I also think of it as: »nah, it's not running anything fancy.« But actually it can amount to quite a lot and there is not much left of 4GB RAM even though I usually use it with GalliumOS and Firefox which is a bit more aggressive with memory management (you should stick with Chrome OS though!).
Edit: on second thought, I cannot imagine making good use of more than 8GB with your usage patterns at the moment. I had a laptop with 16GB for two years, not used for gaming or hosting more than one virtual machine, RAM was just rather cheap at that time.
From the point of view that a Chromebook is a piece of computer hardware with a keyboard and a 10-15 inch screen that runs a webbrowser to display websites it may look like 4GB are sufficient. At the moment.
The best way to find out if 4GB is enough for you would be open Chrome's Taskmanager during your usual desktop browsing and check how much Chrome consumes. Some extensions also consume additional RAM, websites tend to grow and be designed more responsive, also people usually have several tabs open or pinned. 4GB is okay for now but on top of my head knowing the browsing habits of people around me and my own and that a Chromebook may well last 5 years or more while being regularly updated with security updates and new features(!), I'd recommend to spend a bit more money to get an 8GB model at least.
From another point of view I have watched 2GB Chromebooks and HDMi sticks suffer under the load of poorly written iframe Grafana & Kibana madness for months. You don't want to run out of RAM if it can be avoided.
Chromebooks also feature Android Apps and Linux apps (Crostini). It is still not a full fledged desktop experience like a Mac or Windows computer but you certainly have the possibility to make use of more than 4GB RAM now or in the future. Some people may argue that you could close some rather unimportant tabs or that the browser should manage background tabs better but I don't think that is a good solution as you may want to use a split view to view more pages at the same time, work with multiple monitors (small portable monitors exist) or just have the information ready when you need it (and no network access).
The benefit is to not run out of RAM, which results in significant system slow downs. Also typically RAM cannot be upgraded on Chromebooks. I'd give the same advice for Chromebooks as I'd give for any laptop that you are going to use the next couple of years: 4GB RAM is not enough, get 8GB and have peace of mind.
Edit 2018-09-12: There is another point to consider: the processor.
To keep it simple: try to avoid Intel processors where the model number starts with an N.
These are out-of-order low power CPU designs and different from typical mobile CPUs. They have been marketed as Atoms but also as Celerons and Pentiums. If you can afford to spend more money get a device with at least a Pentium processor without an N in the model number, or even better an m3/i3 or m5/i5. Intel has been very liberal with names and letters which is very confusing for consumers after some generations/years.
Google is likely going to present a successor to the Pixelbook in a few weeks. Keep your eyes open you may find a good deal for the old model. If that's not an option you can check reddit where a user posts a Bi-Weekly Buying Advice Thread, here is the latest one at the time of writing: https://www.reddit.com/r/chromeos/comments/9ci9bd/biweekly_buying_advice_thread_sep_2_15/
I live in Germany where Chromebooks are rather unpopular, so there isn't much advice I can give where to get the best deal in your region.
Final note: I also do have a Lenovo N22 with said Celeron N processor, It gets work done (it's the one I tortured with iframes) it's just not that kind of device you were initially looking for, a convertible for a bit more than $500 and 8GB should be a good choice for the next 5 years.