TWRP no RamDisk - i didn't patched the "Stock" TWRP via magisk to flash it onto device, btw i'm calling it "Stock" TWRP
i know this command but i think it's will not add RamDisk for su perms
i have installed it successfully :|
and no, when i just flashed the boot.img it didn't gave mee su perms
No fastboot command will "add ramdisk". ramdisk is something some "systems" include, it is involved in the process of booting; really it is just a way to make a filesystem available. A system that has been packaged with a ramdisk might only use the ramdisk briefly before switching to some more substantial, more traditional filesystem; but it is possible that after booting the ramdisk filesystem is still available. It doesn't really matter.
The "fastboot boot" command might let you test a boot image (or a recovery image -- any image that is the first step to booting a computer) without installing it. Whether it works or not, you haven't changed your system, the next time you boot you are back to the "old", installed, system.
If Magisk is installed in the recovery partition, you might have trouble installing TWRP. One approach is to *not* install TWRP, and just "fastboot boot twrp.img" when you want to use TWRP.
When you plan to install Magisk in the boot image, you can test the patched image with "fastboot boot magisk-patched-image". You will never bootloop because the patched image will only be used once -- if there's a problem, there's nothing to uninstall.
I have lost track of what problem you are trying to solve.