For example, taxing landlords enabled more young people to buy where they had help from mum/dad because more for-sale stock in the market, yet it hindered those renting (with no help from mum/dad) because lack of rentals, their rent went up and made it more difficult to save for deposit.

Exactly. Multiple and “opposing” things can both be true.

Also, max value of home needs to be £450k. I am sure tonnes were penalised for just because they couldn’t find the home in the right price bracket.

No.
www.worksinprogress.news/p/the-failur...