I was wondering... If, for some reason, I will be stuck in bootloop,

I was wondering…
If, for some reason, I will be stuck in bootloop, and I need to enter twrp recovery for restoring a backup, how would i do that? All those watches have one button, and I just know to enter recovery from system, and as far as I know, adb commands are not working with phone off.
Also, which would be the most effective way to have a system backup for safety reason, if something goes wrong with flashing and modding?

You have to enable usb debugging and connect to pc. then run adb reboot recovery

Yes but as I said, adb should not work with phone off or in bootloop. Am I wrong?

Ahh yes - sorry - you are correct. I can not actually think how you would get out of that problem without flashing firmware

Yeah I was thinking so. But just to know, in the case of flashing the stock firmware, I would lose the twrp recovery, and I should repeat the whole process for rooting, right?