A direct answer is that a MacBook Air 15" is more suitable for your use case.
Please consider this:
there is absolutely no urgency to make this decision.
Your MacBook will still be supported by Apple with security patches until roughly
October this year. Once this runs out, you can just use Chrome or Firefox, which will receive their own security patches, so you'll stay secure still. This will give you 1-2 more years. After this runs out, you can use OpenCore Legacy Patcher to upgrade to Sonoma and have 1-3 more years of Chrome or Firefox upgrades. For your use case performance-wise this will be fine.
I have the same laptop and I've absolutely no desire to spend £1,800 to replace my machine, which works very well and will stay secure for 3-5 more years. I also have access to someone who has a 17% discount, but this doesn't make a major difference.
For the fan noise, just buy TurboBoost Switcher Pro for $10. It allows to turn off TurboBoost of your processor. This will make the laptop silent for 90% of your listed tasks without any perceived performance degradation, assuming you're keeping it on an even surface.