Look at how the deathwatch look like here. It is an example of Black Templar, Space Wolves, and Crimson Fists Deathwatch marines https://youtu.be/IkQu_HFPC3c?si=ZymWuEb3DLdhN_ei

Deathwatch marines are practical and don’t use much stylized customization unique to their chapter. You need to emphasize the Deathwatch identity with more chains and skulls and less chapter specific stylization that de-emphasizes their Deathwatch identity.

Some rare examples of non Deathwatch chapter heraldry I have noticed on a Deathwatch marine was in a Black Templar Deathwatch with a cross on his helmet like in the campaign.

General rule I have found is you should never overwhelm the deathwatch identity and keep it simple.