As far as I know,[famous last words] the Host Computor adapts each a/c type for speed. I also understood that it adapted climb performance as well. Yes, the final [requested] Flight Level must be input.
At EGCC we have directive as to who files how high to where.
eg, EGBB/CC/NM/GP etc to EGAA, FL240. into EIDW, FL220 [I may have got those the wrong way round
]
Soutbound, HON FL as requested, except if cruise level [if higher] can be made 50 DME/MID. Then we have the EBBR inbounds...
EGCC, FL290/HON then FL330 for cruise, then FL230/BIG FL190/VABIK for EBBR!
I know that it's as clear as mud, but I'm doing my best
we aim to please, it keeps the cleaners happy