Macs prior to System 7.0, we don't know if it even works. The other part of the puzzle, MacPPP, can be downloaded via charm.net. MAC PPP connections have proven out well, once the configuration was complete. We will add more specifics on MAC PPP when we can. You would need a very fast 386 or better running MS-Windows to make use of this.
More memory makes it run better.
There is an inherant limit of 19.2K for the modem connection. This has proven out well, if just a bit slower than otherwise, with a 14.4 modem. The book is great. There is now quite a bit of freeware, shareware, and public-domain software out there now. The Internet Starter Kit is another book we have found recently that provides the Netmanage sofware.