The thing is hobbyists like to experiment and are drawn to the roasters where there's an option.

With the same roaster of two different type drums, even with the same time-temperature relationship, the roast will be different. It is not the "thermometry", but the perforation allows more infrared heating, and the "burning" of molecules at the bean surface that impart difference. The penetrance of heat and the subsequent vapor front and condensation and Maillard reactions will be different. This different heat transfer phenomenon is observed for example in fluid bed vs drum roasting; the temperature can be similar, but distinct flavor and aroma. The perforated vs solid drum is just another example of difference energy and rate of transfer.

Like the previous analogy, steak grilled vs pan fried vs broiled over the same fire. Which steak do you like?

This is a simplistic question, I know. But if I'm thinking of installing a perforated drum in a TJ-067 gas roaster where that hasn't been done, will it tend to allow batch sizes on the small end of the range or make roasts with small loads more prone to tipping? They offer that drum in their electric roaster.

Burners are pretty close to the drum, I would suggest seeing if they have a IR Burner..
The gas controller doc.s that were posted says its for a IR Burner..