Hi Dan
Yeah, I read large parts of the Sutta Pitaka. There is a fairly complete German translation online at palikanon.com.
For English, I think you have to buy dead-tree editions if you want to read every last sutta. If however it is not your ambition to read every single sutta, the selection online at Accesstoinsight.org is quite good, as far as I am able to judge. Last I checked, that site has a slight bias to towards a western secular audience, leaving out the painfully detailed descriptions of, for example, the hell realms. No big loss in my opinion, as we have ample tradition of the hells in our own western culture. They largely coincide, too, FWIW.
As to a guide to the texts... I just started reading. After some time, resistance to the convoluted, repetitive style of oral transmission died off, and it became an interesting daily practice for a few years. But then I'm a geek for old texts. YMMV.
I started with the Middle-Length Discourses. I finished all four of the "major" sections (middle, long, grouped, factored), and read most of the "little" texts as well.
You may find, like I did, that the summary presented in MCTB is quite accurate, it is a good tour of the Buddha Dhamma. You may still find it to have been worthwhile to read the old texts, because they are nowhere as smoothed out and unified-looking as a summary like MCTB. It's like reading the Gospels and noticing things like how only John has all the "I am ..." quotes, how there are two different genealogies for Jesus in two different gospels, both of which lead to his step-father ironically; how his last words were reported differently and so on. All of these you will miss if you only consume some harmonized summary.
Maybe you have a taste for hairsplitting over minute details, and then comparing parallel suttas (such as
Bahiya and
Malunkyaputta Suttas) will be right up your alley.
What is your fear regarding "getting lost" or "running in circles"? After all, it's just a huge corpus of old texts. They can be read sequentially, like Game of Thrones or the Lord of the Rings or the Iliad or the Bible.
Maybe it would be a good moment to ask yourself, what do you want to get out of this project?
Edited to addI can't really comment on commonalities/differences between AF and Theravada. As far as I am concerned, the doctrines presented in the Suttas are not the unified monolith which later commentaries, and the Abidhamma, make them. Thus contrasting "The Suttas" with the AF Trust Website is not very meaningful in my opinion.
Cheers,
Florian