I suggest, if you have all drivers open source, then secure boot and fast boot can be enabled, but if you have Nvidia drivers or some proprietary blobs like Wifi, then disable it
If you are booting with secure boot without any issues I would leave that on. In terms of fast boot this is a Microsoft thing which basically keeps the hard drive in sleep mode, it effectively never turns off, hence fast boot times of Windows 10/11, and also prevents booting off other media.