Part 23 and below are 15m / 49ft
Part 25 is 10m / 35ft.
They are certification requirements for declared TODR.
They are mandatory minima for public transport planning, they are recommended for non public transport planning. I don't think that changes much as you cross the Atlantic. Legally for a private flight you can use TORR, or frankly press your luck and hope your handling skills are amazing, then explain it to the insurer later.
Europe does add additional safety factors (1.3 for take-off, 1.43 for landing) which are not used in FAAland.
If there's a separate rule for IFR departures I missed it in my EASA and FAA IR courses, but I may have done.
G