NAT for LAN PCs with Failover

RouterOS General
1

I am working on a failover configuration. Usually I do

/ip firewall nat
  add chain=srcnat out-interface=ether1 action=masquerade

to NAT the PCs out to the internet. This forces everything out ether1 though.

I have found that this works with failover:

/ip firewall nat
  add chain=srcnat action=masquerade

Is this correct?

2

No.
If you have two wan interfaces the answer for sourcenat is detail each separately.
OR
If you ahve added both to the wan interface list then use the interface list WAN.