If I had to choose between those two offers, I'd go with Devers. Maybe he takes $300M/12 to lessen the AAV, and who knows, maybe he'll be a useful DH years 9-12.
There is a top limit, however, and maybe both of those numbers are too much. Spending $500M on both seems impossible, and unwise.
One might get this for $500M:
$140M/6 Nimmo
$140M/6 Swanson
$70M/4 Diaz
$60M/4 Contreras
$30M/3 Eovaldi
$30M/4 Wacha
$30M/4 Fulmer