the faster the chip.....The quicker it can die?
Yes, or well, sort of...
Ultimately this depends on many details of how the chip is designed, and how it's fabricated, which are usually a closely guarded trade secret. But for a general high-level picture of chip fabrication, it's common to talk about the chip's transistor channel length, in nanometers. As a general rule, small numbers mean faster transistors. Sometimes this number is called "process node", which is really just jargon for talking about different fabrication of chips. Sometimes the 1 quoted number is called "feature size".
At the extreme high end, most of Intel's CPUs today are 14nm, and 10nm & 7nm are on the horizon. It's important to remember this number isn't the entire picture. For example, some chips are using 12nm or 10nm transistors, but the achieve only slight improvement over Intel's 14nm, because this one number only captures 1 spec about the chip fabrication.
When Freescale announced the Kinetis microcontrollers, 90mn with a particular type of flash memory process was advertised. Since then, they've been reluctant to give any info about the fabrication process used. As far as I know, Teensy 3.2 and 3.5 are using 90nm. What size transistors are used in the chip on Teensy LC and 3.6, I do not know. I suspect the K66 chip on Teensy 3.6 may be using something like 65nm, but that's really just guesswork. We also don't know for sure what size is used in the new chip for Teensy 4.0, but there's reason to believe it's 40nm, mostly because so much of it is so similar to their iMX6 chips which were previously advertised as using 40nm.
As the transistor size (or really, the channel length which is distance between drain and source) shrinks, generally the transistor is able to have lower on resistance when the same voltage is applied to the gate. With digital logic, usually propagation delay is mostly determined by the transitor's on resistance and the amount of capacitance on the wires and gates of other transistors it drives. Generally the rest of the stuff in the chip also grows smaller, so capacitance also goes down, again giving faster performance for small sizes.
But there are tough trade-offs to be made. As the transistors get smaller, there's a lot less surface area for the gate to electrostatically couple to the silicon below. So smaller & faster transistors require incredibly thin insulation between the gate and drain+source. The thickness of the chip's oxide layer puts an upper limit on the voltage the transistors can withstand. There are many other trade-offs, especially regarding power consumption and heat, which also drive these modern chips to require lower voltages.
The finer details are a huge and complex subject. Sadly, much of this stuff is shrouded in secrecy these days. Searching for info is also quite difficult, because the internet is filled with articles written by business analysts (or I supposed you could call them by other less charitable terms) who throw around phrases like "process node" without the faintest idea of how a mosfet transistor really works.
But as a general trend, faster chips tend to be made with smaller transistors, and the reduction in size tends to require lower voltage and gives less resilience to damage if accidentally exposed to higher voltages.