We've a public range with a subnet mask 255.255.255.192 so 62 IP's and the default gateway is the 1st IP in this range so for say
192.168.0.1-192.168.0.62 the gateway is 192.168.0.1

We currently NAT the entire range, but are looking to have part of the range using NAT and part with NoNat (i.e. stuff behind the router is on public IP).

Is it possible to do this on an IP by IP basis or would we need to move the IP's that we want no-nat to, for example, the top end of the range or have the incoming feed on 2 ports with one natted and the other no-natted.

We'll be using vlans on the private side so will have 1 vlan with NATed machines on private IP's and the other VLAN with public IP's that will need direct mapping through. I'm assuming this is possible? We could dedicate switch ports on the green side to each machine with a public IP if required

We're looking at the 1100AH so we'll have plenty of ports available.

You can do this if the ISP splits the range and uses part of it as a link network and the rest as a routed network. In many ways it would be easier if the passed you the existing range to you via an additional /30 link network.

We just get the IP's presented to us currently...

Previously a sonicwall was used and the IP's we wanted NO-NATed were bound to the auxiliary interface and then we passed those straight through...

I'm guessing we could do the same on routeros? just bind some of the public IP's to port 0 for NATing and some to port 1 for NO-NATing?

It depends on which functions of RouterOS you want available. Somebody else on the forum ran into the problem that they had multiple ranges from their ISP and because they were essentially bridging the IPs to the clients the inter-routing among the ranges was happening at the ISP via the link rather than locally at the router.

If you only have one range you could bridge ports and still use the IP Firewall.

We only have 1 IP range presented that want to split up and use this way.

Hmm... My mistake. Just been told we have a routed subnet... so first IP is the network, second is the gateway which is not on our equipment.

We're going to split the subnets as it seems the simplest way forward.