Alright so this is a quick test for you guys and the results are quite good

4 fights (with 0 buffs, with Chriku buff, with Chiriku+Minato buff, with Chiriku+Minato+Earth Main buff)

so 0% resistance, 40% resistance, 80% resistance and 120% resistance

Also keep in mind that the tests were vs Edo Hiruzen so the damage you see is a bit blurry and it's 3x the same number

Pay attention only to the numbers on right side of the screenshots

1. 0% resistance buff

3361 damage taken

2. 40% resistance buff (Chiriku)

2556 damage taken

3. 80% resistance buff (Chiriku + Minato)

1928 damage taken

4. 120% resistance buff (Chiriku + Minato + Earth Main)

1636 damage taken

Conclusion:

0% vs 40% vs 80% vs 120% resistance buff

10083 vs 7668 vs 5784 vs 4908 damage taken

(keep in mind Edo Hiruzen mystery is 3x the same numbers so what I wrote here are the actual numbers in those fights)

So having 120% resistance buff literally halved the damage, from 10k down to 5k