#26 & 30 I use Firefox all the time with 43 tabs open and right now 4 windows open. I have a Intel Core i5-4690K 4 core CPU @ 3.50GHzand 32gbs of memory and a Gigabyte motherboard from 2015. No issues.
I modified the look and have multi row tabs.
https://davidswebsite.com/Firefox_tabs/firefox_tabs.html
Yes, there is another way to obtain MTRs but I found that The Patcher works well. A blessing, thank God.
Note that you can run multiple Firefox portable installations (customize one, then clone, but use thus each for its own general purpose) yet you need to place a copy of the FirefoxPortable.ini from Other\Source to the main folder of FirefoxPortable and edit the FirefoxPortable.ini to AllowMultipleInstances=true DisableIntelligentStart=true