I prefer not to use bios mod to not lose warranty if I need

You have to understand that with bios mod you are flashing the bios of your card, on hardware level and with MorePowerTool you'll modify the values of the software on Windows, so your Windows will read the values of MorePowerTool, without need to flash the bios, you just need to use the program and restart your computer

I suggest you to read: https://www.igorslab.de/morepowertool-amd-radeon-rx-5700-und-rx-5700-xt-tweaking-and-overclocking-software/

There's plenty of information on Youtube too

In my case, I didn't touch the bios and my card is doing 54Mhs, it's good enough for me, I don't want to take risks to achieve 56Mhs, but it's up to you