The rendered clip stutters just as badly, even when viewed in a media player.
There should be absolutely no preview issue in this situation, how can Vegas possibly choke on a 10 second clip with nothing else on the timeline? My guess is there's something quite wrong with the codec of the rendered clip.

When you use TP from inside Vegas the frame rate is that of your project. The Project settings menu item is not relevant. The values displayed when running inside Vegas are not changeable and are possibly wrong.

When you run TP standalone, then the values in the project settings menu now have meaning and you can change them, and they show proper/correct values.

Try disable the cache feature, make very small modification, then do render again.

"When you use TP from inside Vegas the frame rate is that of your project".

No, as I said, it's not. The resulting file is clearly at 29,97 fps.
The reason i'm actually trying to work with titles directly rendered from titler pro is that in my experience so far, Vegas is totally incapable of smooth rolls inside its title generators.
I know there's other, better methods such as creating long png files in photoshop and panning them , and Bob has explained the mathematical problem of the stuttering in another post of mine around this issue. I just thought NB would possibly handle this in a better way, as you can creaty things in NB that you cannot do in photoshop. I'm generally not all too happy with titler pro 4, and often end up creating my own titles with vegas tools.

"No, as I said, it's not. The resulting file is clearly at 29,97 fps."

As I said, those project settings have no meaning when inside Vegas and the export to MOV function is always using those settings. Newblue does not expect you to export a MOV when running TP from within an NLE. Run TP as standalone and you can change those project settings.

The generated media on the Vegas timeline from TP clearly uses the Vegas project framerate be that 30p or 60p.

IMO it is wrong of TP to export to MOV, from inside the NLE, with the unchangeable default project settings. They should disable that menu item inside an NLE to not confuse people. TP should export to MOV with the NLE settings when inside an NLE. They don't but you can work around this quirk by running TP standalone when you want to export a MOV from TP. Here you can change the settings, including the frame rate.

Thanks Norman, after some back and forth emailing with NB they finally said it's a bug they're now aware of. They also suggest to "disable GPU for transitions" to see if that gets rid of the stuttering roll. I'll try that later and post what I find..
The strange remaining issue though is still the weird rendered file that Vegas is choking on so badly that it drops the playback framerate to 18fps when playing a 10sec .mov file that TP exported.

update:
this is what media info says about the file exported from TP as a standalone app, set to 25p 1080p:
Format : MPEG-4
Format profile : QuickTime
Codec ID : qt
File size : 69.5 MiB
Duration : 8s 0ms
Overall bit rate mode : Variable
Overall bit rate : 72.9 Mbps
Writing application : Lavf54.59.106

Video
ID : 1
Format : PNG
Format/Info : Portable Network Graphic
Codec ID : png
Duration : 8s 0ms
Bit rate mode : Variable
Bit rate : 72.9 Mbps
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 25.000 fps
Compression mode : Lossless
Bits/(Pixel*Frame) : 1.406
Stream size : 69.5 MiB (100%)
Language : English

72.9 Mbps seems huge, Vegas cannot play the file without a framerate drop to 17-18 fps in preview. I'll try an export from V13 and see how they compare.
Oh and the rolls are stuttering, still.

MOV files rendered from TP are basically image sequences of PNG files stored in a Quicktime container. PNG supports alpha which the text output needs and PNG is super high quality but it can be hard to playback.

I don't seem to have a problem with rolls. They are smooth. I've tried some tests after reading your post. Playback can be a little touch depending on the preview mode. I normally run in Preview auto during edit. Auto results in a setting of half since the preview window is, well, about half size for 1080 projects. The caching that TP4 can do should make any playback smooth regardless of how complicated the TP project is. There is also ram preview in Vegas when a TP4 project cannot playback at full framerate. Long rolls can render slow and playback drop below full framerate.

Maybe you have playback problem(s) in general on your system. I've not tried importing a TP rendered MOV on my system but I can shortly.

edit: a 1080 29.97 MOV from TP4 plays totally smooth on my installation.

I do NOT run or own NBTitler 4, however I do use all earlier versions of New Blue Titler and have always used .png sequences for a given number of reasons. Png offers very good quality, but it can be system resource intensive as has been suggested by others in this thread.

I never depend on the given workstation being able to play sequences at proper video rates as it can be so touchy. In order to do quality control of such a render, I use a DI like Cineform codec or Magic YuV made from the sequence to test video display rates and performance with Vegas timeline.