I spoke with a Firefox dev, I was told that due to accessibility settings, multithreading with touchscreens wouldn't come until the current Beta build is released to stable. Technically it should already work on the beta build but it doesn't seem to work for me.
AFAIK, accessibility support, including touchscreens, should be enabled in Firefox Beta 52 now:
https://wiki.mozilla.org/Electrolysis#Schedule
In the meantime, you can force Firefox to enable multiprocess, even if you have a touchscreen by creating a new about:config pref "browser.tabs.remote.force-enable" = true.
`about:support` will tell you if the multiprocess windows are activated, depending on the add-ons you are using.
The E10S indication is probably not supposed to be user visible. You can check it though:
Go to about:support page and in the first page, check the Multiprocess Windows row.
And for those that look at about:support and see it's disabled for some reason (an add-on you use doesn't play nice with it is the common thing), you should install an add-on called Add-on Compatibility Reporter, to tell you which one is causing you issues.
A lot of FF is hare-brained, though. E10S solved the unresponsive UI for me, but for the life of me, I don't know how to enable it on my touchscreen Dell. There is no indicator in preferences that tells me whether it is on or off and no button to simply force it.
Javascript-heavy websites tend to burn through the CPU of my Macbook Air, but I don't know how to throttle background tabs. Or at least profile which tab gobbles my cycles. About:performance is not that helpful. Ideally, there would be some indicator if a background tab eats more than x% CPU.