@Falko:
now to the questions:
can i use multiple CARP VIP as a base for a 1:1 NAT? (i need 10-20 1:1 NAT ip addresses)
Yes.
@Falko:
is it more useful to use multiple default gateways (iproute2) in the linux machines or a set of shared LAN CARP VIP? (one for each VLAN)
Having multiple default gateways on the Linux machines will introduce complications unless you're doing policy routing within Linux. Without policy routing, you'll have issues because only one default gateway will be used, and that will route return traffic out the wrong way in some cases. Single homing everything is easiest for that reason.
@Falko:
do i need a specific switch support/configuration to enable the in/outbound CARP VIPs? (i have a cisco switch)
If it's a real Cisco switch and not a Linksys Cisco, should be fine. The Linksys Cisco switches at times have security-related settings enabled that break multicast. It's also possible to break multicast on a real Cisco switch but such configs are very uncommon.
@Falko:
i using LACP ports with CARP a problem?
no, lots of people do that.