Switching to ARM doesn't result in lower memory usage unless:
- The developers use this transition to optimize their code
- There is a specific optimization in this particular use case that was not possible on x86
But in general, nothing changes in terms of memory usage. If your browser is currently a lot, it's not going to change. However, most modern browser don't actually render the tabs you're not looking at, so opening even thousands is possible.
Also, if you do run out of memory, the OS will move the least used data to the SSD, so the result would be that there is going to be some small delay when you switch to this app/tab/etc and data needs to be moved back to memory. So you switch to app 2, app 1 moves from memory to SSD (to free up space), app 2 - from SSD to memory. If his happens occasionally, it's not that big of a deal. But if you are really using
actively all your memory, this will happen every time a program access the RAM and would result in a terrible performance. But if you see that Chrome uses 20GB of RAM, most likely most of it it's not being actively accessed and can be stored on the SSD without a problem.
So because RAM is usually cheap and applications are using more and more, it was a very cheap insurance that you don't end up in this situation now or in the future. But at 200€+ it becomes more of a question if you actually need it. But not because something on ARM is different, but because the pricing is different and it changes the balance of pros/cons