For complex switchings I've found that is best/easier to use a software named Bome's midi translator, which works flawlessly with softstep. Together they can do whatever you want.
Answering specifically your question (I also do play the guitar) I have a patch in softstep/bome midi that works the following way:
Buttons 1-4 - Each button alternates between red and orange led everytime you press it, and contains two amp presets (I'm using s-gear software), let's say, for button 1 two clean presets, button 2, two break-up point presets, button 3, two crunch presets, and button 4 two lead presets.
Everytime you press one of this buttons it switchs to the right amp and turns the previous amp led off. If you press the same button, alternates between the two prests. If you press different amps, it always recalls the last one used in that button.
Buttons 6-9 are "stompbox effects" (compressor, overdrive, reverb, and delay) and work independently of any amp choice. leds are green and light on/off individually.
button 0 gives me tempo feedback from DAW and works as tap tempo
Button 5 starts/stops songs in DAW
In my case, because I feel that midi translator is more flexible and easier to work for my needs, my modlines are pretty simple: basically they just send a simple CC or PC, and all led control, switching, etc is made via Bome's
so.... short answer, yes it is possible to make softstep work the way you want. and if there's something you can't do with the modlines, you can always go the Midi Translator route