Thanks, I am using "MSI B450m Mortar Max". My ram kit is not listed on the website as compitible for my motherboard but works fine.Yes, if you're using custom timings based on the calculator, then you'll need to configure them manually. Otherwise, XMP may override your manual settings, though it depends on the motherboard software.
Yes, I can change timings whilst using xmp profile. Is it better to use xmp profile or keep it off?Seems this is one for which you can receive different answers from different sources, likely for different boards.
On my MSI Tomahawk X570 I have XMP on, and then can manually overide the settings I wish to tweak.
For example, I turn on xmp. It goes to 3600MHz Memory and the SMP timings etc. I manually change the memory frequency down to 3400MHz, and it happily stays that way through reboots etc.
Yoir MSI board uefi may work differently to mine in this respect, but I doubt it!