I wouldn't be worried about buying AMD in terms of thermals, their laptop CPUs are fine. Usually, it's the WiFi card that poses the biggest problem in terms of driver availability, in which case you can purchase an Intel WiFi card from Amazon for $15-$20. Battery and "optimizations" depend on your config and distro. Most plug-and-play distros should be fine OOTB, if you're setting up Arch from scratch I assume you don't have a problem in looking for drivers/compiling code.

Edit: I personally do not suggest that anyone buys a new laptop unless they do not have a choice (horrible used market or the like). There is a heavy mark-up on new devices and the used market in the West (especially in the US) is excellent if you're OK with fiddling with some parts of your laptop (or not - sometimes you don't even need to do that). But being in c/linux that's about granted, eh?

I saw some Reddit posts claiming AMD being not optimized for Linux particularly for arch related distros (I use EndeavourOS)

This is literally the other way around.

But in general it depends on the budget. Both Intel and AMD work perfectly on Linux. It's more about the CPUs themselves. AMD is better in the budget category because of much more capable iGPUs and performance/price ratio but Intel is better in high end because of simply better technological advancement (as long as you can keep the chip cooler than 90°C).

But if it keeps working for a long time, like 6+ years, then I don't mind investing.

I wouldn't be so optimistic about modern laptops, especially ones with dedicated GPUs. They don't live for more than 2-3 years without repairs.