As far as 'overkill' for a 100Mhz probe used on a 20 Mhz scope,no.
>You would not save anything by designing a probe solely for low BW scopes.
>One hint;use the shortest ground lead you can get by with.
It's possible that some HF probes might not have the C adjustment range at the high end to compensate some LF 'scopes.
Best regards, Spehro Pefhany