@tk
Bike 2 is a 24" bike with 3x5 gearing that has more parts but it's like how Bike 1 was before removing all parts: cheap steel or aluminum, mostly broken plastic and a helping of rust, but it almost seems to work.
The shifters and brakes have seized up in general. The rear derailleur and chain are thickly coated with rust, but it feels like more than WD-40 and wire brushing will be needed to make the really stiff chain and rear derailleur

The current goal of this one is less of a great blank slate than Bike 1, mostly to make it run again. This has meant removing the front derailleur but keeping to a 1x5 type setup. The bike came with 20"(?) wheels and big 1.5" tires, but again, switching to larger but relatively bigger 26"/650b/700c rims and thinner 38c/40mm tires sounds about right. I'm willing to replace the chain (already have a new one), but I have a sense that replacing any more parts will be paying more money than this bike is worth right now.