Assamualeikum, Is it better to fast the siyaam of Dawud 'alayhisalaam, or to fast the siyaam of Dawud 'alayhi salaam with the white days and Monday and Thursday?

There are 2 sayings regarding this, and I think that the stronger saying and Allah knows best is that u should not add to it a constant day to fast like every monday, but u can fast ashora or arafah for the non pilgrim as these are rare occasions.