UPB is the standard, which the Omni supports great. Just turning on and off lights is easy. You program them with UPStart on a PC and control them with the panel. You can control Simply Automated switches, PCS switches or HAI switches.
That is pretty basic. If you control a SINGLE light with the controller, it will know the status of the light. If you manually switch a light, it can tell the controller the status.
Now, PCS, the company that developed and licenses UPB came out with Gen II and Gen III. Simply Automated switches don't support that which restricts the use of a repeater. Some people like Simply Automated switches and I have used them, but keep in mind they use an older version firmware. In any case, the panel can turn on and off any generation. Most other brands of switches like HAI are Gen III.
UPB is great but it has some limitation. One is, when you use a "scene" sometimes called a "link", the panel loses track of the status of the switches. A link controls many lights at once, so the switch status is NOT always maintained correctly. This may cause problems, but that is another story.
Because of this, Leviton created HLC. It is a way that HAI has set up its UPB network. It has several advantages over basic UPB, with one being status of switches is maintained. Another is that the panel can actually program HAI UPB switches without a computer. A final benefit is that if you use HAI room controllers and House controllers you can do more. I think a Omni IIe can control 8 rooms of lights. A "room" is a logical grouping of lights.
You tell the panel UPB or HLC in the setup. In HLC mode, the panel scans the switches to get their status. In UPB mode, status checking is something you have to do in programming. The negative of HLC is that it dictates a certain numbering and naming scheme, and some features only work with HAI switches.
So if you don't plan to have many switches, you can use UPB. If you have a larger house, and want some status tracking, use HLC. By default, HLC works great with HAI switches. Some added features work with non-HAI switches, but only when you manually program them. The panel can only program HAI switches, so the others you have to program them with UPStart using special information.
Last house was Simply Automated switches and UPB. This house is HLC and HAI switches. My current house is much more sophisticated and was much easier to set up, but you need to learn HLC, and follow the rules, so really, its your choice. If you take the time to learn HLC, it adds a great deal to UPB, but only a few of us here use it. I myself would never not use it if I had the choice. Its just made my lighting much nicer.
> And regarding Upstart...do I need a separate PIM that connects to my laptop directly to use?
You don't HAVE to, but its a really good idea.