Unless in the case mentioned before, with anything magic (spells, summons, preparations, etc.) Force.is always the limit. For spells, rituals and summons, Force is the only thing that matter for the Drain Value.
The type of damage however is decided with the number of successes (after limit is applied): less than your Magic, it's stun, more it's physical.
In case of spirit summoning, the Drain Value is twice the number of successes rolled by the spirit when resisting summoning, but the type of damage is once again determined by your number of successes (and not net successes). Note that when summoning, you can't use reagents to set the limits.
Oh and there's another case where you have to be careful with limits, it's when you are aligned to the background count, you add the BGC value to your limit.
And, speaking of background, note that in the barrens, there is always a BGC of at least 1, often 2. And, there is of course Matrix noise you have to deal with. I think it's always 2 but I'm not sure.