The Plus units (I, II, III, IV, and X) are all manual-only triggers. They cannot be used for power control of a remote light, as they only pass along the sync signal. The Plus III and IV allow for group on/off, but not power control.

For power control, you'd need TTL triggers (Mini TT1 and two FlexTT5s), and for each non-TTL light, like a B800, you'd also need an AC9 adapter for the FlexTT5. This is expensive.

But it's not the only solution you have for remote power control from the camera.

There are also the RadioPopper JrX and Jr2 triggers (the receivers can control the ABs by the RJ11 data port).

And, of course, Buff's own CyberSync triggers: the Cyber Commander transmitter and the CSR+ or CSRB+ receivers. Which are built specifically to work with Alien Bees, White Lightnings, or Zeus units via the RJ11 data port; the Einsteins have their own (cheaper) plug-in unit, which gives you the most control. Quoting from the Buff website:

Cyber Commander™ allows control of parameters from the camera position, including the status of recycle beepers, slaves, modeling lamps, and even power adjustment. It enables manual bracketing of individual lights or a group of lights in precise 1/10f digital steps, while automatically updating the meter reading and power levels. For setups containing lights with different wattsecond ratings and model lamp wattages, the Cyber Commander™ will adjust proportionally, allowing you to maintain deadly accurate what-you-see-is-what-you-get (WYSIWYG) preview.

Granted, all this is going to be more expensive than manual-only triggers, but also a lot more convenient. It's up to you if the additional cost is worth it.