Opera 3.62 (I was unaware of 3.64 if it wasn't a typo) works pretty well for the modern web still, rendering maybe 20% of pages fine, and 30-40% usably - with knowledge of HTML you can navigate 80% of pages or so, but that involves reading the source for links and then pasting them in. The runner-up would be IE5 for compatibility, and while it renders some things better, it's highly crash-prone when it finds something it doesn't like, whereas Opera will generally keep going.
Arachne is the best DOS-based browser, being compliant with most modern standards, but that's not Win3x.
As for using a Pentium to run Win3x - perfectly reasonable to me - there's 16-bit Win3x apps that benefit strongly from a Pentium, like Zombie Wars, so it's not unreasonable.