Your rx5700 going over 100°C ? That's crazy mate, how do you sleep conveniently in the night? Just because it's working doesn't mean it's safe, a gpu running at that temp can cut lose all it's memory chip and you will start getting memory size error, don't do it 😔
Doesn't matter, I have many GPUs in a small area. Not much I can do about it. I have never had a GPU go down because of high temps. I do have 3080/3090 that thermal throttle, so I added extra cooling for them and fixed the problem.
1. The software will it shut down if too hot. So its safe and within OEM programmed limitations.
2. I have 3 year warranty. If it breaks, ill just RMA. But have many GPUs running at excessive temps for many years, and never had an issue.