A guide to the interaction of critical rate modifiers

Don't think there's a topic that explains this, yet.
Crit buffs are buffs that set your critical chance to a certain rate. Simple enough still, but the topic gets more complicated once we get to the interaction between different crit rate modifiers. So i'll cover a few different scenarios here.
All info on abilities/SBs is obtained from Enlir's spreadsheet.

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First off though a bit of info on crit rate. The base crit rate of your character is actually decided by your weapon. It can range between 0% and 5%, though the one that is used by far the most is 3%. There are trends between weapons, like Fists often getting 5%, but they are in no way absolute.
Fun-fact: there is one accessory in this game which has a base crit rate of 3%, making the highest possible base crit-rate 8%.
Critical damage is a 1.5x damage modifier and since it's only the end-damage that changes, it is unaffected by stuff like the ATK soft-cap and can reward a great boost to damage if you already have very high ATK.
For the purpose of the detailed scenarios below i will be assuming a base crit rate of 3%.

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Scenario 1:
I have two normal crit buffs (e.g. Ydas Internal Release and Jechts Ultimate Jecht Shot) and use them both. In this case, both are normal crit buffs with the status ID 614. They overwrite each other, so be careful and use the stronger buff last !

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Scenario 2:
I have two crit buffs and one is a custom-parameter buff (e.g. Jechts Ultimate Jecht Shot for a normal 25% 614 crit buff and Aurons Bushido BSB for a 6005 ATK +30%, RES +25% and 50% crit buff). So if you know about IDs, different IDs stack and that still holds true here. Both will be applied to the character, BUT the game only uses the higher crit rate. So in this case, even if Jecht's SSB was applied later, the game would still use Auron's BSB 50% crit buff as long as it is active.

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Scenario 3:
You use any crit buff, but an ability that you use has a built-in crit rate (e.g. Exploding Fist or Clouds BSB commands). In this case it's actually quite simple. The game still uses the highest crit-rate. So if e.g. you have a 25% crit buff and use Clouds BSB commands (80% crit), the game will simply use the 80% crit rate. If you however use it with Exploding Fist (20% crit), the game will use the 25% crit from the buff.

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Bonus scenario:
In the future, we will get Critical Damage buffs. Ramzas SSB2 is the first version of this buff that is party-wide, though Amarant SSB and Delita BSB feature an attack variant that is a bit different. Their attack (as in the BSB cast) has a +50% critical damage bonus, that (thanks DeNA) stacks additively with the +50% critical damage from Ramza SSB2 for a total of 2.5x critical damage.

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Thanks to:
u/Enlir and u/ElninoFR for giving me the additional knowledge, that i needed to make this post.

Previous guides from me:
A guide to terms and abbreviations,
An explanation of the elemental scale and
A guide to stacking and status IDs

Feel free to give me feedback and correct mistakes :)

~Scytherman

P.S. Notice how i said i will be assuming a base crit rate of 3% ? Notice how it never got picked up again ? That's because it gets ignored if a crit buff is active anyway, since all existing crit buffs are higher :P

P.P.S. Fun-fact 2:
I always call those IDs "status IDs", but thechnically they're called "Status Ailment Type", regardless of buff or debuff. That would be very confusing for some players though, since "ailement" indicates something negative, so "status IDs" is what i use.