So my wife has a 10 year old low end notbook. 500Gb of storage (HDD), 2GB of GDR3 RAM, and an intel Celeron Processor N2806. It originally came with Win 8, then she “upgraded” to win 10 and after that it was pretty much unusable. I am talking CPU and Ram about 80-90% in idle, opening a browser got everything down to a crawl. She mostly used it a storage and brwosing, watching youtube and occasionally to write. So I (also a Linux newbie) finally got the time to install a newbie friendly Os (Fedora) and it’s so much better! I am Talking 20%CPU usage and 50%(?) RAM in idle.
A thing you didn’t mention to improve thermals is to take it apart remove the dust from the cooler and maybe change the thermal past, that laptop came with windows 8 (released in 2013) literally 10 years ago.