The heat off of the 2015 MBP is no joke. I'm surprised people remember it fondly, despite the keyboard. I'm pretty sure the heat that thing put out could cause infertility. The most recent MBPs are much better in this regard (excluding the i9 pre patch).
If anyone's thinking of doing this, I'd highly recommend Thermal Grizzly Kryonaut paste. I got a 10C drop in both average idle and load temps after replacing my MBP's stock paste with it, and significantly better battery life, though I don't have any hard numbers for that. This paste usually wins in benchmarks and it's only outclassed by liquid metal. It's $13 on Amazon for a gram, which was enough to do two laptops and two desktops for me.
The heat problem is a major issue across the laptop industry (and all in one desktops with a small tightly-packed case and a PSU inside the case -- Mac mini is another big offender). You aren't getting the CPU/GPU performance you paid for because the laptop traps heat and the CPU throttles itself.
IMO this is ripe for class action lawsuits.
Generally, buying a high performance portable computer is a bad idea, because of thermals.
