I am quite confused about how I should play my ranges in these spots on the turn. 

My flatting range in this preflop spot against a 2.5x open probably includes suited broadways, pocket pairs up to TT, suited aces and some offsuit big aces, SCs. 

I will get to the turn with all my pocker pairs, flopped pairs, sets and maybe the bigger aces. On the turn he bets 2x pot so I would need to defend 40% of my range here to avoid getting exploited with any two and QThh would be quite high in my turn range .

Although in practice, the particular villain is likely to be doing this with a very strong range of combo draw and nut hands and it could be correct to fold here with QT. 

However, my question is how should I approach this spot in a vacuum?

Many thanks for your kind replies :)