yes
yes, as long as the default policy for forward is drop/reject.
You cannot have 2 active gateways the way you have. Only one gateway has precedence and that one is used for traffic coming from lan or guest vlan. To really achieve your goal, you need to do Policy Based Routing and you have 3 options:
- mwan3 package
- pbr package
- a set of rules/routes for each internet connection.