From someone elses question, who was trying to sum the maximum value in each row of two columns, I found this:

=ARRAYFORMULA(SUM(IF(B3:B>N3:N,B3:B,N3:N)))

which works!

but i need to apply that same process to a subtotal, so i can make use of its ability to only sum rows that are not hidden. unfortunately i cannot get this to work, it errors on only accepting a range as input:

=arrayformula(subtotal(109,IF(B3:B>N3:N,B3:B,N3:N)))

tried to apply array formula and the if logic to subtotal, getting an error