Like Dave, I am running on a much lessor laptop than you (and Dave). Two gigs ago, I was performing with a Bass, Acoustic Guitar, and Electric Guitar, running thru Focusrite, into C3, and mixing amp sims, fx, and Piano/Organ VSTs out without a hitch. I do not use “cpu hungry” synths live. Many discussions on this forum about not using the resource hogs:
I feel there is more going on there than just buffer settings. Try using the resource monitor inside C3 to detect what plugs are killing your system, and use lessor ones.
BTW…What guitar fx are you using?
Are you using a latency monitor?