Temperatures and damage are modeled. Time here is sped up a lot; real damage takes weeks or months of use.
The model holds resistance fixed. A real loose joint oxidizes, heats more, and can end in a fire.
The red line is the wire insulation rating, 90°C, 334.112. NM ampacity uses 60°C, 334.80(A); terminals are 60 or 75°C, 110.14(C).
Torque screws to the maker's value with an approved means, 110.14(D). The trade uses a torque screwdriver.
Hands-on work is done with the breaker off and tested dead (trade practice). Setting the screw loose stands in for years of use.
One wire per screw unless marked for two, 110.14(A). Splices need an identified connector, 110.14(B). A loose splice heats the same way.
Feeding through the screws is allowed on a two-wire circuit. A multiwire circuit's neutral must be pigtailed, 300.15(B). Many electricians pigtail anyway.
Push-in holes are allowed only on 15 A circuits with 14 AWG solid copper, 406.10(3).
Most home rooms need AFCI protection, 210.12(B). An AFCI looks for arcing, not heat. A joint that only runs hot will not trip it.