Does 'N/Query' module, suite analytics have functionality for Multi level joins ? Unlike save search where we are limited to single level joins only.

Yep. You can have as many joins as you want

just one more question? currently which is faster in terms of performance, saved searches or query module?

They both cost 10 units, so I believe, basically the same

Generally speaking queries are faster then searches

Perfect. We will shift from searches to query modules now. Searches are making unnecessary complex code for us. With query it will be simpler to get what we need. For now we are doing, creating first search, Then itterating and creating few arrays. Then passing those arrays in filter of next search filters.. Thank you for the replies.