Call process and task rest APIs of camunda process engine from another standalone web application

Process engine services are same for all the deployment models/application setup.

Of course, yes. You can follow the standalone deployment model (remote server approach). In that you need to add camunda rest dependencies, so that you can access process engine services via rest-api.

Refer this camunda architectural section for remote server setup:

standalone-remote-process-engine-server

Architecture Overview | docs.camunda.org