Read the part where it says you can't set OI's if you instant result genius
Mate, FMT mode was designed in a way that your assistant manager always set Opposition Instructions for you before every match and there's no option to turn it off(such option is present in the full mode).
When you play FMT Mode in normal way(without using Instant Result) then you have a ability to "clear" your assistant manager's Opposition Instructions before every match and set yours Opposition Instructions instead of his OIs but when you play FMT Mode with Instant Result then you always play with your Assistant Manager's OIs and you can do nothing about so the decisions of your assistant manager what OIs to use affect your results with any tactic that you use.
I'd say if you play with Instant Result then OIs is the least thing that you should worry about because there are many other factors which affect your result more than OIs:
1) When you play with Instant Result your assistant manager might change the roles of ML/MR/AML/AMR/WBL/WBR positions in your tactic.
2) When you play with Instant Result your assistant manages makes substitutions during matches and I find very often he makes very poor decisions that decreases your results.
3) When you play with Instant Result then you can't have "Hard Tackles" PIs active for all positions in your tactic because you can't manage the tackling settings of the position during matches so it also decreases your results.
4) When you play with Instant Result your assistant manger doesn't use any Waste Time Tactic which also decreases your results.
As you can see when you play with Instant Result there are many other things that might greatly reduces your results more than OIs and I find that all that might reduced your result up to 20-30% but with a good tactic you still will overarching despite all these issues and with Instant Result you'll be able to achieve all your goals but you shoud be ready that to do that you just need to a have a bit stronger team than if you played in normal way and that's all.