Lets talk about how laptops just dont cut it with todays Photoshop requirements

How fast an application opens is rarely a great measure of anything. What it probably will measure the most is the speed of storage, because application startup is mostly about pre-loading code and assets, and pre-caching scratch files and anticipated data into RAM. For an application such as Photoshop where significant portions of startup involve the Home screen and verification of licensing and availability of online services such as Adobe Fonts, Creative Cloud Libraries, and Cloud Documents, startup time may also be affected by the responsiveness of your Internet connection.

If you’re concerned about Photoshop performance in general, and trying to choose a system, it seems like a much better idea to run the PugetBench Photoshop benchmark test, and then compare your results against their list of the other systems that have submitted results. What score does your system get?

Another thing about application start time is that, at least on the Mac, there are two startup times: 

• Time to start the first time after computer restart. 
• Time to start every subsequent instance after the first time after computer restart. 

The reason for this is that after computer restart, all caches are thrown out, so a starting application must build them all from nothing. If you exit and then start that application again during the same system session, the second and subsequent times it should start much faster, because the system still holds the caches.

You talked about heat, but if you’re talking about app startup, that takes so few seconds that on any modern system, there should not be time for heat to build up to the point that the processor hits its critical temperature and throttles.

Anybody have a laptop that opens photoshop in 5 seconds?

By @RAB123

Yes, my two-year-old MacBook Pro opens Photoshop in 5 seconds…if it isn’t the first time starting Photoshop since the last system restart. If the Mac was restarted, starting Photoshop takes a few seconds longer.

The main reason is, as you say, cooling. There's no way to effectively cool a laptop, so components are throttled down to avoid meltdown.

You might ask why they put these components in there when they can't run at full speed - but it's a great sales argument! Customers will take it at face value.

Another thing is vendor modifications to the operating system and drivers. This is something they do to put their own stamp on the product. They want you to buy a Dell/hp/Acer/etc - not a "Windows" laptop. These modifications are usually not done with high-performance advanced applications in mind, but to satisfy the "average" consumer and/or gamer.

All these extra layers between Photoshop and the OS/drivers is what causes most problems.