Does installing too many appExchange apps on Salesforce instance has any impact on performance of that instance? I mean every app will have its own triggers or automation and thus consuming power/limits of Salesforce in some way. Any suggestions/ thoughts?
Managed packages will consists of triggers, classes , objects and many other components and UI .
Performance On CPU - Note that code from managed package share CPU with your existing apps and hence can potentially impact performance .Lets say you have a managed package that has a trigger on account on insert (lets hope its written properly) then apart from all other process you have this will also run and consume CPU.
However if lets say app has trigger on its own object then this may not impact the CPU .
Note that trigger is an example and any other process automation (like workflow or process builder) also consumes CPU allocated in a context .
Performance on Data Storage - Managed packages will add additional objects and hence storage could be hit if the objects in managed package consume lot of storage ( has LDV Objects)
Apart from that Managed packages that have gone through salesforce security review process and passes have its own governor limits .
We cannot generalize that installing many packages will cause performance issues its more around what do these packages do and how they work that should be analyzed to infer the impact of the managed packages .