Some questions regarding ripple counter and 74HCT
Yes, you need bypass capacitors. Otherwise the rail collapse puts the internal latch behavior at risk.
The onchip capacitors --- gate-bulk, drain-well, drain-bulk, metal-metal, metal-bulk, etc --- are not large enough to provide the "crowbar" current often seen as gates transition between logic states.

I'd just tie the unchanging pins --- Preset, etc --- to the appropriate rail and be done.

To demonstrate the effects of prop-delay, implement decoders to recognize one or more of the states, say 0000, 1111, 1010, 0101, 0110. Notice all the tiny (100pS?) glitches.