TIL that on Firefox you can unload tabs from memory without closing them
The feature is called Tab Unloading, and weirdly enough they made it not easy to access despite its usefulness.
You basically have to type about:unloads in the address bar and hit enter. If you then click on "Unload", it will put the least used tabs to sleep. If you keep clicking that button until it's greyed out, you'll have unloaded all your tabs from memory.
This feature is handy if you want to temporarily switch to something that is memory hungry without having to close your 100 tabs.
I'm pretty sure that Chrome does this automatically. When I work I usually need about 98,000 tabs open at a time and often I don't actually click any of them but I need them.
Anyway I will often open a tab and have to wait to it for it to load. But I've played around with it and I don't seem to be able to get consistent results so I'm not sure what parameters it's using.
This reads like the dystopia in which every piece of software got replaces by a proprietary web application by some evil mega corp. What you need is at least a mail client and a word processor.