I feel like your first question is flirting with the concept of ICM. You can read more on that
here. One component of ICM is that even though a decision might make you chips in a tournament, it might not make you dollars. Therefore a decision that's always profitable in a cash game, isn't always profitable in a tournament/SnG setting. So the answer to your first questions is quite complicated and probably depends on the spot. If you double up, are you now in a dominating chip lead? This is likely a profitable call. Are you doubling up from 4th largest stack to to 3rd with 5 players left? Might just be better to fold and wait for some other folks to go broke.
I personally think that a lot of folks overestimate the value to be gained from implied odds and it's heavily dependent on your position in the hand. Usually I start from the direct pot odds and work from there. With one card to come, you've got ~20% to complete your flush. If a flush always wins, then you can break even by calling a bet that is a fifth of the pot. E.g. If Villian bets $10 into a $40 pot, Hero now has to call $10 into a $50 pot (risk 10 to win 50). Hero will approximately break even in the long run by calling in this spot. Now, what if Villian bets $20 into a $40 pot. Hero now needs 33% equity to call here (risk 20 to win 60), which they don't have with just the raw equity from the flush draw.
But if Hero thinks they can get Villian to put in additional money on the river when they complete the flush, then they might the able to profitably call here. That's what implied odds are. How much do you think Villian will put in after you complete your flush? Usually you can get Villain to commit chips more reliably when you're in position as you give them a chance to bluff and can always bet if they don't. Other things like board texture and stack size can affect implied odds too.
