We have a deployment where we have 20 branches (as phase 1) we want to deploy Meraki MX on each branch. Our servers are on worldposta cloud. We want to deploy SDWAN solution. So please recommend the best scenario and best deployment. Also can we deploy a virtual MX 100 on the cloud or no? if no is the solution will be workable for SDWAN without a cloud MX?
So there are a couple of points to this. You can absolutely utilise SD-WAN for your intra-site traffic. Best design depends on traffic flows. Within AutoVPN (meraki site-to-site VPN) you can utilise a hub and spoke full mesh topology - just depends on if you need traffic routing between all of your sites.
For the vMX, however it is only supported on AWS and Azure at this time. You could use a 'non-meraki vpn' (traditional IPSEC) from each brach MX to worldposta. This configuration is very easily done as you configure it at a 'global' level within your site-to-site VPN configuration.
vMX are really only available on AWS and Azure at the moment as VMare instances, although I am sure something will be in the pipeline to expand that.
Auto-VPN from Meraki dashboard could handle connections into the worldposta cloud. Details on the site mention VPN capabilities so there should be no issues with that connectivity. Of course Auto-VPN can only really sort out your Meraki gear and VPN config on the cloud would have to be with their support.
It won't be pretty, but it will work.
P.S Consider the throughput and max tunnel count the worldposta VPN can support Tag your MX branch sites accordingly to assist with excluding certain networks from all attempting to mesh with the worldposta cloud (if it can't support it)