Multiple .war’s in an Web Application Server (e.g Tomcat, JBoss) vs Multiple Applications with Embedded Servers (e.g. Springboot)

Hello,

We currently have a JBoss application server running say 20 .war web applications, which is getting overloaded. We have a load balancer already splitting the load between multiple hosts, but this server is still starting to struggle.

We're open to a range of options, ranging from splitting these large sever out to different servers/hosts, to changing them to be containerless standalone applications such as SpringBoot.

Theres plenty of information/research about the pros and cons for doing this for single applications, where I think running one SpringBoot application tends to be more efficient than running one application server with a single application due to having less overhead, as well as much easier deployment. However I can't find anything about doing this in greater numbers and have some queries.

1) If we scale this up to say 10-20 SpringBoot applications, would each one having their own embedded Tomcat instance instead be less efficient than a single application server with multiple applications?

2) Is it easier just to have more hosts and spread these out?

3) Is there a nicer way to share common configuration between these applications? I'm familliar with svn externals, but git doesn't seem to have as much support for subrepos.

Thanks!