The number of snapshots in your template shouldn't matter. Once you push an image from a template snapshot a clone is created which in itself doesn't have snapshots and thus shouldn't suffer from the performance penalties of VMs with snapshots.

Use VMware OS Optimization Tool for cleaning and optimizing the image.

Check if your AV solution has some sort of VDI operation mode. This should allow you to run it in a way that works with machines the get deleted and recreated without having problems with AV client management due to duplicate IDs.

I usually configure software and settings changes completely through GPO... Every couple of weeks I boot the template to push the changes to it, create a new snapshot and push the refreshed images to the pools.

From time to time I create a new template from scratch by deploying from MDT just like I do with physical PCs except for a few changes to the MDT task sequence like installing VMware Tools, Horizon Agent, AV in VDI mode and so on...