I'm not familiar with sound of real amps.
We'll get back to that.
What would be some good models to start with that have a nice full range clean sound that
would work for guitar and guitar synth with octave down
Search YouTube for videos by Leon Todd, Cooper Carter, and Marco Fanton. They cover these topics well.
In addition, search the Wiki's
Factory presets page for "clean", as there are a number of presets that are good candidates. In addition, many amplifiers that people associate with metal, heavy rock or progressive rock or jazz, make wonderful clean amps by dialing down the input.
Also interesting in the edge of breakup "category"
There isn't really an amp category I'm aware of that is "EOB", it's just how we (mis)treat a particular amp. "Edge of breakup" is something that happens when we push a clean amp hard, or a "rock" amp to the very edge of distortion so that a little bit harder strum or picking will cause distortion just as backing off will cause it to clean up again. SO many of the factory presets do that, and there are many ways to get there.
Back to not being familiar with the sound of real amps… It's important to have an understanding how real amps work when working with a modeler, because a modeler is almost always a digital version of a real amp. FAS modelers have an incredible amount of depth that scares people who don't know what makes amps, speakers, and effects, tick, so give yourself time to learn, fiddle with stuff and ask questions.
"
Amp and Cab modeling for beginners" is a starting point, as is reading the manual cover to cover several times. The
Blocks Guide is also useful. There are other manuals associated with the FAS modelers that are essential information but they can wait.
Cooper Carter has a great, highly recommended,
video series that teaches how to use the modeler from the basics to advanced.