I just want to add to this.
I have a companion Windows PC for running Omnisphere and a few other plugins, and Timbuktu between Windows 7 and OS 9 was too choppy and slightly buggy for my needs.
I've been playing around with different server/client combinations, even going as far as trying Java VNC viewers on the old MRJ/JRE1.x that Apple provided for OS9 (it was not pretty!) and I have found my personal "goldilocks" configuration:
Server: TightVNC 2.7
Client: VNC Viewer FAT (otherwise known as the AT&T VNC Viewer client beta2) - the filename being vnc-3.3.2beta2_mac.sit.hqx, which I found here:
http://cns.utoronto.ca/ftp/pub/vnc/Having tried VNCThing, on the surface it looked like it was going to work fine until I started playing around with some VSTs hosted on the Win7 machine - it seemed to be failing to redraw parts of the screen and click and drag behavior had a 50/50 chance of working or causing mayhem.
This older VNC client to my amazement is actually working with a very smooth, very impressive framerate, and clicking/dragging so far is not a problem. This is (was) a beta version however, so there's every chance a bug might come up that I haven't found yet, but so far so good!
I have not played around with any options on the client - it is using hextile by default and so far its working so well that I don't feel I need to try anything else. For the server however, I had changed the screen polling cycle to 30ms - as low as it would go. That could be an indication of why its working so smooth.
I did have trouble finding this VNC version, so if someone has a way to preserve this file somewhere more reliable, please do it ASAP!