Hi,

Q1- I am searching for the best way to document my own poker strategy (preflop, postflop, different stack-size, etc.) so that it would be easier to maintain and use?

At the moment I am using flowcharts for this purpose, but I am searching for better solutions/tools.

Q2- Is there any place I can find poker strategy Templates or written poker strategies to get some ideas from?

The best place for you to learn and improve your skills is our community. Here you will find everything you need.
https://www.cardschat.com/poker-strategy.php