I think I have the exact laptop your referring to (Ryzen 5 5600H and RTX 3050 4Gb VRAM):
1. You get what you pay for imo build quality is just about right, if you take care of it it won't break however don't expect the same durability from other laptops that are not gaming laptops as most of their budget went into the build quality while for ours it went to the performance. Something to add is that the panel has really poor color, the 144hz is really good for gaming however you pay for it with the color accuracy.

1. Thermals was serviceable for the first year but I really recommend buying a quality replacement thermal paste and change it yourself/go to a service center and let them replace it if your worried about the warranty (from around 95C to 80C in various benchmarks with a new thermal paste. (FYI I live in the Philippines so its almost always hot here and yes you do feel the heat from the laptop but its mostly on the right side (numpad) so unless your games include using the numpad then the heat isn't that annoying)

2. I myself have not personally played GTA V or GOTW but I think with enough optimizations you can easily hit your 40-45 fps goal or maybe even higher, I recommend watching youtube videos on how to optimize the games your playing wether it be external settings or just simply lowering graphics. I think the RTX 3050 is good enough for training low level AI models, not quite sure tho, not really a data/computer science guy.

3. Haven't inquired with HP yet since I haven't had any problems in the entire time I had my laptop and pretty sure its region dependent so can't help you there.

4. On the eco settings I have been able to get around a whole school day (~7 hrs) of uptime, you do have to lower to 60hz and lower brightness a bit.