As Feathers says, the fare is a zone 2-6 one. If you travel via Paddington using contactless then you will be charged the same fare because there is no other defined. If you use Oyster then you’ll be charged the same fare from Notting Hill Gate to Heathrow, but on the way back you will be overcharged if you touch out at Paddington. If it is a blue adult Oyster without a discount then you will get the overcharge back a few days later, but other cards will not get adjusted.
If you want to avoid being overcharged then using the internal passages from the Circle to the Bakerloo and then the Elizabeth line is indeed a way to go. I don’t think TfL will add a via Paddington option because it can be circumvented quite easily.