Help with a telephoto lens choice for my canon R10

Hi I recently bought a canon R10 and was thinking about telephoto lens for motersport, plane and wildlife photography. I posted here a while ago asking about the ef 100-400 mkii vs the RF 100-400 however after more looking I have realised the price of the ef mk2 100-400mm and realise that it just wont be doable for me as it is still used £900-£1,000 in the uk so, I was leaning towards the canon RF 100-400 alot. But before I do, is that a silly choice for what I want to do or Iam I missing anything in the £500 - £550 telephoto market?

Many thanks in advance.