Hi Vishwanath,
Having so many parameters definitely will add to the performance, not just from parameters angle but from number of event handlers created as you said 1 FO can have more than 200+FUs. Best way to avoid performance issue is to having a good archiving and/or deletion plan as soon as you are done tracking like last event or expected event is posted.
Regarding number of parameters on EH, we had lot of parameters ( serial numbers ) in one of our project and we split them into control and info parameters to make it lean. This will depend on your situation/desing on when and how you are using these parameters like Ruleset/preprocessing/UI which typically impact the performance.
Thanks,
Vishnu