Large Scale Analysis updated workflow for PAT 3.2.0?

Is there any tutorial (or) module to find out how large-scale analysis can be performed using the Openstudio web interface? The information in Github talks in general rather than specifics of Urban level analysis

Also, would like to know other tools (preferably open-source/trial) to carry out urban building energy modeling hassle-free

This may not answer all of your questions, but if you have not yet I would start with the URBANopt documentation. You mentioned PAT in your title which is the Parametric Analysis tool. That is for a large scale analysis of a single building for calibration, uncertainly, sensitivity, optimization, etc. URBANopt is designed to model multiple buildings, and support OpenStudio and EnergyPlus along with a number of additional simulation tools.

New to the latest URBANopt release which followed OpenStudio 3.2 is support for the OpenStudio Analysis Framework (OSAF). This uses the OpenStudio Meta CLI that is installed with PAT. So for the purposes of URBANopt, it uses elements of the PAT Installation but not the PAT Interface. This workflow is described here.

Hope this helps.