That first link is from 2018 so not really helpful because FF releases new versions every 4 - 6 weeks. Whatever was mentioned in that thread is for a different version of FF.
Note the last link starts out by saying: Mozilla's Firefox browser does an excellent job providing stable, fast performance with a minimal memory footprint.
Start FF in safe mode; that means all addons disabled. Help then select Restart with addons disabled. Keep an eye on the memory usage. If it remains low, probably one of the addons is causing the problem. To troubleshoot which one, enable 2 of your addons and browse. Keep enabling 1 or 2 at a time until you notice the usage spiking. The last 1 or 2 you enabled is probably causing the issue.
Note the last link starts out by saying: Mozilla's Firefox browser does an excellent job providing stable, fast performance with a minimal memory footprint.
Start FF in safe mode; that means all addons disabled. Help then select Restart with addons disabled. Keep an eye on the memory usage. If it remains low, probably one of the addons is causing the problem. To troubleshoot which one, enable 2 of your addons and browse. Keep enabling 1 or 2 at a time until you notice the usage spiking. The last 1 or 2 you enabled is probably causing the issue.