Electrical – Switching to LEDs: 12v LEDs on existing transformer or remove transformer and use 240v LEDs – Which is better

Wow! You can use the screw in type LED bulbs, which contain their own controllers. These are typically dimmable down to about 20% using standard wiring. Here, we have Cree bulbs that look VERY similar to old Edison (tungsten) A19 bulbs, rather than the funny looking futuristic LED's. They're also much cheaper than the older screw-in LED's, about $8 each for the newest type. I don't know if they're available in your area. I LOVE THESE BULBS. ref: homedepot.com/p/Cree-40W-Equivalent-Soft-White-2700K-A19-Dimmable-LED-Light-Bulb-with-4Flow-Filament-Design-BA19-04527OMF-12DE26-3U100/205597080

If you're going with low voltage, (12V) you can use the LED strips and get rather creative, rather than using standard lighting fixtures. I replace fluorescent tube lighting with LED quite often now, for instance, or you can use them in an area with a diffuser panel below, as is typical in kitchens here. Friend of mine did the same with his bathrooms. I've also seen them used inside a paper light globe, wound in creative spirals and such, to make a unique decorative touch. Also consider using the strips as they were originally created to be used, as under-cabinet lighting. Be aware, however, you can't have a dimmer on the AC voltage side (before the transformer) and will have to use dimmers supplied for the 12V LED strips. I've seen these with remotes, and that's probably your only option for those. On a side note, the LED strips come in various color outputs (Bright white, Red/Green/Blue (for accent lighting or novelty lighting,) Warm white, etc.) The multicolor ones do require the specialty 12V controller to get all the effects.

While most 110-240V LEDs are nasty complex loads due to their AC/DC power supply, many 12V LEDs are probably no more complex than the LED and a resistor, or possibly the LED, another diode or 4, and a resistor for 12VAC service. That sort should run fine of a 12V supply at full ratings and with no need for a regular halogen bulb in circuit.

If your 12V LEDs are straightforward "bulb replacements" or devoid of a power supply circuit between the 12V supply and the LED, they will probably behave as above - after all, when the halogens you put in circuit burn out, that's where you'll be anyway. If they have a more complex power supply, the manufacturer would be the best bet to determine the correct deployment on your power supply. In all likelihood, they will be fine.