Best practices of converting an already created site into Craft CMS? We have various clients who already have websites but would like us to optimize them a little bit and set them up on craft.

Is there a more efficient way to do this than just hand coding all of the PHP and blocks for every page to align to be editable on craft?
If you're not already on a CMS, I'd recommend migrating to Craft sooner rather than later. Sounds like you're definitely planning on migrating to Craft, so I see no valuable reason to delay.

Pros of migrating now:


Awesome Craft features, like Matrix
Plugins
Twig


Cons of migrating later:


More legacy code to port
More legacy data to restructure


You'll notice that both of those lists reinforce the idea of migrating now. ;)