Tony,
There are still some installation conflicts, but a large portion of JBoss tools can now be installed into MyEclipse 2018 – I believe some of the JBoss dependencies have changed, and our integration of JBoss tooling has changed somewhat as well.
1) We have integrated some of the Wildfly connectors, so if you try to install those from JBoss tools, there will be conflicts. Would recommend simply taking our connectors in this case, and avoiding the installation of the connectors from JBoss. We are already working on the Wildfly 14 connector, and that should make the next release.
2) I believe the BPMN modeling capabilities you need can now be found here – they install into MyEclipse 2018 just fine, and support the JBoss Business Process Engine.
https://marketplace.eclipse.org/content/eclipse-bpmn2-modeler
If you re-try the installation, can you see if it now does allow you to install the tools you need? Perhaps you just need the BPMN plugin from the marketplace now?