The different iterations of the TRWW devices all have slightly different heat up times. I have the 14mm terpcicle and the 18QC and when I switch between the two it takes me a while before I can dial in the timing.
I would be surprised if your torch is too big for the 18mm as it is one of the larger TEDs TRWW makes so it can take a large torch. I use a big buddy size torch with the flame set in the middle of the range. I would not focus too much on torch time but rather heat it gradually and take test puffs as each torch will be different. As soon as the flame starts to turn orange I generally stop heating but sometimes it is hard to see the color change if I am in a sunlight area so I err on the side of caution and under heat it. You can always add heat if if isn’t producing a satisfactory level of Vapor but you can’t remove it if you are close to combustion.
Another thing to bear in mind is that the vapes are heat builders so they draw more and more heat into the bowl as your session goes on. The second and third draws are going to produce more Vapor than the first. With this in mind if you are getting any Vapor on the first draw I would stop and wait to see where you are in 10 seconds or so. Once you have got this down you will get the feel of it and have a good idea of roughly how long it will take with the settings of your torch.
Finally there is also an advanced heating technique that you can also use which produces even more consistent Vapor. Basically it warms everything gradually and minimises the temperature differences between heater and bowl. This means it’s easier to hit the sweet spot and produce thick Vapor from the start.
Hope this helps and enjoy.