This is a nice starting point for a guide, however it seems like it's still a work in progress. It only mentions the very basics of the Inca civilization, yet doesn't elaborate on how to use these advantages properly. Being so flexible I feel that any Inca guide should include optimal game play plans, since so many are viable. For example: you can go with the standard 4 city tradition opener into a rush towards Rationalism without huge investment in culture to go for a science victory while abusing observatories. Another example: you can warmonger, researching archery first and going for a slinger rush against a neighbor, replacing the famous archer rush, than go wide and use the now experienced slingers and their upgrades to defend all your cities or continue warmongering. The above examples show how to use the Inca's 2 unique advantages(UU and UI) for 2 completely different strategies and show why these advantages are powerful enough to use said strategies rather than something else.
If you want to go deeper you can compare the above strategies with other civilizations who typically use them and show why Inca is still competitive(or even better) than the other civilizations. For example you can compare the typical science victory choices: Babylon and Korea, and show how Inca can match up with them. Obviously it depends on the map, but you can compare the lack of GS for Inca compared to Babylon and Korea to the improved production and the availability of observatories(both thanks to being in hilly areas). You can also expand the guide towards G&K since almost everybody uses the expansion these days. G&K changes the Slinger's upgrade route from merging into Riflemen to going into Gatling Gun and Machine Gun, which makes the Slinger's retreat promotion even better if you can keep them alive until late game. Also the availability of religion allows Inca, as well as all other civilizations, to enhance their strategies even further.