What you described is pretty light usage, people still do that on machines with 4 gigs of RAM with no big issues.
8 gigs would hit the spot for you I believe, but since you'd like to keep the machine for a few years and we don't know what stupid technology becomes fashionable in 2025 that will destroy our RAM just like Electron apps have since 2013, if you can afford it easily, get the 16 GB version. If you can't, don't worry and get the 8 GB one, it will run 100 % today, tomorrow, in a year, and unless your needs change dramatically, it will absolutely be usable after five years.
It's kind of a meme nowadays to go around telling people that your current amount of RAM is the ABSOLUTE MINIMUM, I guess it makes people feel like proper professionals or something, but let me tell you, editing 4K footage from an iPhone once a week doesn't make anyone a power user. Having lots of tabs open in a web browser doesn't make anyone a power user. Starting all apps a person knows how to use at once and pretending like it's their normal workflow doesn't mean they need that much RAM in the machine.
I develop web apps on my Mac and could've gotten the 8 GB model easily and it would work just fine, because my previous dev machine was a 8 GB Dell laptop running Linux (not-so-great RAM management) and it was fine. I only got the 16 GB one because I'm going to make some changes in my workflow that will require more RAM and because the machine is my work tool and pays for it.