Firejail seems to help for that .
Solus is patched as good as it gets according to my tests with the spectre-meltdown-checker but you need to make sure that your Browser does not give your passwords away.
In Chrome based browsers that means activating strict site isolation (recommended way). FF is patched as of version 57.04 via regular update.
I do both (Activate site isolation and FireJail) which is as good as it gets -I guess.
And yes banking with your smartphone....I wouldn't do it right now sine updates are scarce on some smartphone OS's.
Those flaws are extremely nasty - but I am sure Ikey can say a lot more about it.....