Probably not. I’m not familiar with Plesk, but usually things like that don’t work well with things they don’t expect, like Discourse running in a docker container. If it’ll let you reverse proxy to a random port, then maybe. If you were to ask me to do it, I’d do a standard Discourse install, move Discourse to some other port, install Apache and WordPress on a non-standard port, and have Nginx reverse proxy to both. (I’ve also done it without Apache, which is fine if you don’t need WordPress be able to change how your WordPress permalinks work.)
Probably so.