No one uses Strange’s flight mode.
You should.
The best reason being is that it prevents you from falling to the ground when you have nothing on the ground to cover you. In this case, just do Fly -> Y Grace -> Flames -> Teleport. Bam, much safer decent. You can do that without flying, but if you already used another special move, you can fly to do this series.
The other reason being is you can get high/low mixups going. Call a pinning assist, TK Fly, hold down-foward. Then either do a bunch of overheads or just fall with j.S or unfly, and land instantly and do cr.H. Bam, high/lows.
It’s good. 
Does it makes blockstrings safe too? By flying and unflying after Impact Palm? I can’t say if the blockstun from impact palm is long enough to let you fly/unfly safely.
You could, similar to Nova’s flight safety measures. Impact Palm does 21 frames of blockstun, about 29 if pushblocked immediately. Strange’s flight starts up in 22 frames, so you would be -1 if they do not pushblock. It would take 5 frames to make the fastest possible air throw punish, so you’re mostly safe from that. If you just do it to fly/unfly you won’t be at a terrible disadvantage.
Impact Palm to Teleport H is -4, +4 if pushblocked immediately. They would have to pushblock before the 8th frame of blockstun from the palm to get the quickest possible pushblock, otherwise you get even more frame advantage. Palm to teleport L or M is -9. Don’t do it.
If you fly at the (exact) same time an opponent uses advancing guard at any time, you won’t be pushed back, and you’ll be at -1, any later and you’ll be at a greater disadvantage. Unfly will also nullify pushblock and will give you the best frame advantage if you unfly from an air move.
*edit: my bad, advancing guard is 21 frames, not 31. Fixed a bit of math.
