For my hapeneth and learnt from hard recent experience, the term LED transformer and driver tend to be used interchangeably, when they are actually do different jobs. The latter come in constant voltage and constant current and should be used with LEDs designed to be driven as such. You can use a 12v CV driver with a retrofit LED, but they won't dim properly. LED transformers, proper, such as the Varilight YT50LZ have a 12v AC output and work with typical low voltage retrofit bulbs and will dim quite well (if the bulbs are dimmable!). These are the type to use if following switching out the old halogens there are problems - often this is because the existing transformer has a MINIMUM power rating (as well as max), if this is say 20w, you would normally hit that with one or 2 halos at most, but might need a 10 or more LEDs in parallel.
PS Have just seen you pic 35-150W, G4 LEDs are usually around 2 Watts - so you gonna need a least 18 of the puppies to get to the min here.