Re the web browsers I think you're right. You may get away with a more lightweight browser like SeaMonkey or Falkon, maybe like 1 tab of Chromium lol
Distros I'd try on that would be Linux Mint Debian Edition, Debian w/ lightweight DE like LXDE or Xfce, or Arch Linux 32 if you really want to make it minimalist. Gentoo if you're very adventurous but with my EEE PC I found compile times took up to days.
I meant it in the sense of using an obscure operating system to be less likely to be targeted by a threat actor.
Or to be more general, using obscure software for increased security, over actually correctly configuring and using secure software.
Viruses already exist for Linux and have for a long time. They are less prevalent than Windows but this obviously shouldn't be the primary defense strategy for your device.