Best Practice for SS or FS Relationship

Good Day to All,

I have a question regarding the best practice for planning and scheduling.

1. Which one is beneficiary for planning, Finish to Start with negative lag or Start to Start with positive lag?

2. Start to Finish relationship can be used in what circumstances?

3. What about Lags longer than zero?

4. Considering Near critical path activities, how many days can we consider that the activity to be near critical?

5. Considering Total float how many days can we consider to be acceptable? (e.g. 10, 50, 100.....or more than...)

Thanks for your help.

Regards,

Aryan