I'm currently playing around with a PC I built up from random parts, based on an AMD Duron 1200. I have Windows 98 SE on it. It does feel retro. But then I compare it to my 486, and it suddenly doesn't anymore.
Well, both have the same access to the SSL/TLS web: almost nil. With W95 on the 486 with 32MB of RAM and a de-IE4'ized W98 both would be virtually the same except for the speed.
A Pentium II would be a better example for both: Not too old, not too recent. Yet it suits as retro and a usable machine. Enough to render some XVID videos at 360p and 420p with a good video card. Slackware, NetBSD and lot of distros would still run fine. TLS under Lynx and Gopher would still work, the same as a Gopher client.