If I fire multiple SELECT queries(multiple jobs) on the same table at the same time in redshift, will it degrade performance? Is copying to a temp table and dividing the queries between the original and temp table a right approach?
No, as long as your data is sorted and distributed the best way for your workload it's better to query the same table as results are cached. You are fine to fire lots of SELECTs on the same table as long as you're not running other kind of statements like DELETE, UPDATE, VACUUM, ANALYZE, ALTER, UNLOAD or other I might have forgotten, that could potentially lock the table or consume too much resources.
The only real scenario where you should consider creating a copy of your table for querying is when you would benefit significantly from another sortkey and/or distkey.
But have in mind that Redshift is not built to handle hundreds of calls per second, non stopping, if that's what you are trying to do. If you reach the concurrency limit of the WLM queue, queries will get queued while waiting for running queries to complete and you want to avoid long queues at any cost.