So if it is a single channel DMR frequency to monitor, you program it as conventional or TRS?
Will the single channel DMR system have a constant data stream on it?
Or does the data TX only when the PTT is activated?
As always, "it depends".
A single channel DMR frequency could be configured to be used like a conventional frequency with a single set of users (just like the old analog conventional only digital).
However, a single DMR frequency can also be used for both of it's slots effectively becoming two different frequencies. Being DMR, that single frequency can also be configured by the system owners to carry multiple talkgroups supporting different users.
Whistler's implementation allows you to program any DMR frequency as either conventional or as a trunked system.
The easiest thing to do is to program it as conventional. However, if the frequency is being used as more than a simple digital conventional channel, you'll hear a variety of mixed conversations if programmed with wildcards (cc, sl, tgid). Then, for each TGID (at least), you'll need to add another conventional object to "separate" those logical channels.
If you program that same frequency as a trunked system, you can easily tell the radio to store the wildcard TGIDs found as a new talkgroup.
Of course, if the "system" has more than one frequency, you'll miss conversations in either mode of programming unless/until you've programmed all frequencies.
As far as the data - Whistler detects and ignores the data on the frequencies.