It depends on the amount of tabs you have open. I have 106 tabs open in FF and it takes up RAM. Activity monitor lists it at 3.28gb though.

Chrome has separate processes and fewer tabs on my machine. Still summing them up seems to reach 3gb.

IntellJ takes 6gb on my machine so it's the biggest individual user of RAM.

I think parent post might be exaggerating but I have the 64gb M1 Max.