Nah, lower sites and slower research usually has a fairly depressive effect on speed. Less resources, harder to expand (because you don't have the right spells or units earlier, etc.), less means to break particular holdouts or tip a stalemate one way or another, all that sort of stuff. Less mobility stuff, too. You hit critical mass or breakpoints in capability further down the line, spend more time shuttling things around, so on and so forth.
Conceptually not having summoning spam could speed things up, but it... usually doesn't quite work that way, least as far as I've noticed from hearing folks talk about those kinds of games.
That said, if summoning masses are you primary concern, that would be fairly trivial to mod so they're more expensive or otherwise limited. Not something you could just tweak in the options, but particularly if you were setting it up for a slate of specific nations it wouldn't really take all that much effort. Double/triple/quadruple costs, want to say you could tweak things so there's a hard cap on specific spells (though also pretty sure that would take a fair bit more effort), stuff like that. Feeling really frisky you can do some neat stuff with items or units, remove summoning spells entirely (or limited to stuff like the elemental royalty) and have that aspect of the game entirely limited to equipment and the occasional indie or national.