Topics in this episode of OctoPrint On Air, which was recorded on November 3rd:
Full contents with jump marks available in the YouTube description.
The Pi4 has 8gb.
You questioned the benefits for a 64 bit OS. Simple 8gb of usable RAM, the 32bit version is stuck at 4gb.
Certain operations take 2 or more operations where a 64 bit OS can do it in 1 operation. It certain use cases its can double the speed.
The more plug-in you have the more RAM you will probably need.
Also feature creep will, and general changes to the program will slowly consume more memory.
That's not true. The OS is able to use the full 8gb - but a single application might be limited to 3gb.
Google LPAE if you want to know more about it.