Use two layers, first is base rock tamped down tight and properly sloped then a couple of inches of masonry or paver sand. Finally paver sand is used to fill the cracks after the bricks are laid. Do not use pea gravel. The roundness of pea gravel does not allow it to tamp down tight.

You also need a border to keep everything tight.

I have a battery powered Milwaukee but have had cordless in the past. Battery is more convenient but if the charge is low performance will suffer so factor in the cost of two batteries. If just using a few days a year around the house i would go with a corded saw.

Also for a few days a year there's no shame in using a hand saw. Get a miter box and a couple of saws and your good to go. An example of a simple project with hand tools. https://youtu.be/iBfUbQSmMrE

Not an Electrician but I think you can replace the 14/2 with a 14/3 and change out to a two gang box with two switches. That's what I did to our bath fan light combo. I put the fan on its own timer switch.