Given your experience it sounds like I might be needing to look at an 11-32 with sensible sized chain rings and an education in either chilling out or high cadence . I guess as a start point, standard chainsets should be relatively cheap to get going and I can then faff with chain ring sizes later.

Do the maths......

chainring / sprocket x wheel = gear, gear x sprocket / wheel = chainring, chainring / gear x wheel = sprocket.

If 100" top gear, 20" first gear, 11t small sprocket and a 40-406 wheel is ~18.5"-19" diameter.

Then 100 x 11 / 18.75 = ~58 teeth for large chainring.

You should just be able to get away with a 12t drop per chainring.

So a 34/46/58 triple to start with.

And 34 / 20 x 18.75 = ~32 teeth for large sprocket.

Total tooth difference for the chain is 45 teeth.

You'll be pushing the limits of both derailleurs so no guarantees.

But it's probably doable for a 20"-100" range .......

Going 36/48/58 and 11-34 is probably better idea.

The 36/48/58 and a 9-32 Capreo hub lifts top gear to ~120".

But you can fine tune it from here.

Luck ...........